Anti-Magic Shell: This causes a bubble of force to surround the user and totally prevents anything magical from either entering or leaving the shell. It lasts for up to six turns. Shell radius is 5". (Complexity 6)
Notice that the name is actually hyphenated, which is retained up through 2E. Now, some important stuff which will contrast with what comes later: First, it says that magic is prevented from "entering or leaving" the shell; narrowly read, this leaves normal operations inside the shell, such that the wizard can continue casting spells within (e.g., protective spells or items, conjuring an elemental, teleporting away to safety, etc.), seemingly giving more options for the wizard in question. Also, this seems to be in tune with the unique naming of the magic as a "Shell", which seems to imply a barrier defense, with some different content inside. Was that the original intent? Secondly, notice the rather enormous area of effect: 5" radius (which depending on how you interpret that might be 50 feet radius, although I assess it at 25 feet radius in man-to-man scale); this will be greatly reduced in later editions.
Anti-Magic Shell: A field which surrounds the Magic-User and makes him totally impervious to all spells. It also prevents any spells from being sent through the shell by the Magic-User who conjured it. Duration: 12 turns.
Largely the same as in Chainmail, but note some fine details. The description has changed from a "bubble" to a "field" (which in physics "occupies space"; link), and makes the caster "totally impervious to all spells", possibly even inside the shell (e.g., an enemy caster that walked into the shell couldn't cast spells within the barrier)? Also, the wording has switched from preventing "anything magical" to "any spells", which might arguably be more limited (magic swords, et. al.?), but is probably not the intent. Finally, no area of effect is given: note that it's a common Gygaxianism to leave out some of the most important details like that when advancing editions (generally still presuming familiarity and use of the prior work).
Swords & Spells
Anti-Magic Shell: [Range] touch, [Area of Effect] 1", [Turn Duration] 12.
In Swords & Spells, Gygax gives the antimagic shell an area of 1", filling in the gap in OD&D, and much smaller than that seen in Chainmail. This actually might be my favorite and simplest specification for the area, but no other edition will use it. Recall that the range "touch" here is used for all caster-only spells (c.f. polymorph self and so forth).
D&D Expert Rules
Range: 0' (caster only)
Duration: 12 turns
This spell creates a personal barrier about the caster that stops any magic spell or spell effect from coming in or going out. It blocks all spells (including the caster's) until the duration is up or until the caster decides to end the spell.
If we look at this with a magnifying glass, it has some bits of understanding from both the prior editions ("any magic spell or spell effect from coming in or going out"). However, Cook makes it a "personal barrier" (Range: 0', caster only), which is pretty likely how you'd interpret the OD&D text with no listed area, if you weren't also looking at Chainmail at the same time.
AD&D 1st Ed.
Anti-Magic Shell (Abjuration)
Duration: 1 turn/leve1
Area of Effect: 1'/level diameter sphere
Explanation/Description: By means of an anti-magic shell, the magic-user causes an invisible barrier to surround his or her person, and this moves with the spell caster. This barrier is totally impervious to all magic and magic spell effects (this includes such attack forms as breath weapons, gaze weapons, and voice weapons). It thus prevents the entrance of spells or their effects, and it likewise prevents the function of any magical items or spells within its confines. It prevents the entrance of charmed, summoned, and conjured creatures. However, normal creatures (assume a normal troll rather than one conjured up, for instance) can pass through the shell, as can normal missiles. While a magic sword would not function magically within the shell, it would still be a sword.
That's the PHB text, here's the DMG errata:
Anti-Magic Shell: It must be pointed out that creatures on their own plane are normal creatures, so this spell cost upon the Elemental Plane of Fire, for example, would hedge out none of the creatures of the plane.
Now, this version has several changes. It returns an area of effect based on caster level (at least about 12' diameter, so you can probably fit in several friends). It is the first one totally explicit that magic is disrupted "within its confines". The effect also includes defense against breath, gaze, and voice weapon; charmed, summoned, and conjured creatures; and also the effects of magic swords and the like. However, these newly called-out defenses create some possible interpretive problems: If a magic arrow is shot at the shell, does it shatter, disappear, or turn into a normal missile? If the caster moves aggressively against a summoned monster, what happens then? What if a charmed creature gets thrown through the air at the shell, does it physically bounce off or something else?
AD&D 2nd Ed.
Duration: 1 turn/level
Area of Effect: 1 ft./level diameter
By means of this spell, the wizard surrounds himself with an invisible barrier that moves with him. The space within this barrier is totally impervious to all magic and magical spell effects, thus preventing the passage of spells or their effects. Likewise, it prevents the functioning of any magical items or spells within its confines. The area is also impervious to breath weapons, gaze or voice attacks, and similar special attack forms.
The antimagic shell also hedges out charmed, summoned, or conjured creatures. It cannot, however, be forced against any creature that it would keep at bay; any attempt to do so creates a discernible pressure against the barrier, and continued pressure will break the spell. Normal creatures (a normally encountered troll rather than a conjured one, for instance) can enter the area, as can normal missiles. Furthermore, while a magical sword does not function magically within the area, it is still a sword. Note that creatures on their home plane are normal creatures there. Thus, on the Elemental Plane of Fire, a randomly encountered fire elemental cannot be kept at bay by this spell. Artifacts, relics, and creatures of demigod or higher status are unaffected by mortal magic such as this.
Should the caster be larger than the area enclosed by the barrier, parts of his person may be considered exposed, at the DM's option. A dispel magic spell does not remove the spell; the caster can end it upon command.
This is basically identical to 1E, and folds in the note from the DMG as is customary. The name is finally changed to remove the hyphen. It tries to solve the problem of "what happens when the caster attacks a magical creature?", by creating a "discernible pressure" that might break the spell -- personally, that seems a bit clunky and tone-deaf in how an immaterial field of non-magic can create physical pressure on the caster. There is also an added paragraph at the end that introduces two new details: (1) large creatures may or may not be partly exposed when casting the spell (a maybe-or-maybe-not 2E-ism), and (2) dispel magic cannot remove an antimagic shell. Is that a good idea? Does antimagic serve to cancel other antimagic?
D&D 3rd Ed.
Level: Clr 8, Magic 6, Protection 6, Sor/Wiz 6
Components: V, S, M/DF
Casting Time: 1 action
Range: 10 ft.
Area: 10-ft.-radius emanation, centered on the character
Duration: 10 minutes/level (D)
Saving Throw: None
Spell Resistance: See text
An invisible barrier surrounds the character and moves with the character. The space within this barrier is impervious to most magical effects, including spells, spell-like abilities, and supernatural abilities. Likewise, it prevents the functioning of any magic items or spells within its confines.
An antimagic field suppresses any spell or magical effect used within, brought into, or cast into the area, but does not dispel it. Time spent within an antimagic field counts against the suppressed spell's duration. Golems and other magical constructs, elementals, outsiders, and corporeal undead, still function in an antimagic area (though the antimagic area suppresses their supernatural, spell-like, and spell abilities normally). If such creatures are summoned or conjured, however, see below.
Summoned or conjured creatures of any type and incorporeal undead wink out if they enter an antimagic field. They reappear in the same spot once the field goes away. Time spent winked out counts normally against the duration of the conjuration that's maintaining the creature. If the character casts antimagic field in an area occupied by a conjured creature who has spell resistance, the character must make a caster level check (1d20 + caster level) against the creature's SR to make it wink out.
Normal creatures can enter the area, as can normal missiles. The spell has no effect on constructs that are imbued with magic during their creation process and are thereafter self-supporting (unless they have been summoned, in which case they are treated like any other summoned creatures). Undead and outsiders are likewise unaffected unless summoned. These creatures' spell-like or supernatural abilities, however, may be temporarily nullified by the field.
Dispel magic does not remove the field. Two or more antimagic fields sharing any of the same space have no effect on each other. Certain spells remain unaffected by antimagic field (see the individual spell descriptions). Artifacts and creatures of demigod or higher status are unaffected.
Note: Should the character be larger than the area enclosed by the barrier, any part of the character's person that lies outside the barrier is unaffected by the field.
3E changes the name from antimagic shell to antimagic field, borrowing from the text description back in OD&D, and aligning the name with the fact that it's antimagic throughout the volume of space (which was possibly not the case back in Chainmail, but that can be argued). There is additional detail given to the fact that spells get suppressed but their duration clock keeps ticking, and that summoned, conjured, and incorporeal undead "wink out" if they come in contact with the sphere, reappearing later on -- which to me seems even more kindergarten-y and deaf to the literature. Charmed creatures are no longer specifically called out, although I think we can conclude that the creature can pass into the sphere but the charm is then lifted at the time. 3E keeps the no-dispel rule, answers the antimagic-vs-antimagic question (they can overlap with no effect), and also settles the large-creature issue (definitely partly exposed, which seems very strange).
Also this addresses another issue that I'm surprised didn't come earlier: What about golems and similar constructs, who are created by magic, but whose essential power is that they're immune to all magic by default? 3E answers in that they are not affected in any way; an iron golem can waltz in and brain your wizard just like he normally can, a possibly strange ruling, but generally consistent from the point-of-view of the golem's ignoring of most types of spells. Does that seem correct to you?
ConclusionsWhile it's possible to read the Chainmail description as a true "shell" (surface barrier only), such that the wizard can still be casting personal magic inside, this clearly gets ruled out in later editions. As I mentioned above, this has always seemed partly troubling, for what does the D&D wizard have but his spells? In this respect the AD&D spell globe of invulnerability seems seems like a better option, possibly a direct response, in that spells go out but they don't come in (up to a certain level).
In later editions, the effect of antimagic shell was expanded (or further fleshed out) to ban exotic attacks like breath, gaze, summonses, and conjured creatures, but the corner-cases of exactly what happens when those creatures touch or get touched by the sphere caused ongoing complications that seem indelicately resolved (not uncommon in powers initially designed as defenses that get turned around by players for offensive purposes). Note that in theory, even something like the 1st-level protection from evil might have the same issue ("keep out attacks from enchanted monsters", OD&D), but that spell never found need to add the same complications that antimagic shell did.
I might go so far as to ask: What's so critical about disallowing that anyway? Might we not run antimagic shell by allowing the caster to move into range of a conjured elemental or invisible stalker and actually disrupt their presence? That would make for some legitimately potent use from this otherwise questionable spell, and the wizard would need to balance the risk in that they have no choice but to walk out onto the field of battle, with absolutely no other defenses active in order to make it happen (by virtue of the non-magic effect, of course). It could be used in magic-trap-sweeping capacity, as well (otherwise not prohibited in any edition).
Other questions: Do you see the spell get used much in your games? In what tactical situations does it get used? Would it be a better option if the casting wizard could still use personal magic inside the shell? And what's your preference for the effect it has when contacting summoned, conjured, charmed, or magically constructed monsters?