OD&D Sup-III, Eldritch Wizardry, has an interesting "Alternative Combat System (Addition)" (p. 5). Basically, the intent is to turn all movement and attacks during the round into always-continuous and simultaneous action; it introduces the concept of six "segments" to each round. Fairly large tables are presented for missile fire and movement by segment; missile fire and spell sequence is based on Dexterity, modified by a large number of factors (the source for Holmes' initiative mechanic?). For example, if your modified Dex is within 5-9, then your shot will take place on the 2nd segment of the round. If you have a move of 9", then your character should be moved 1½" in each of the 6 separate segments per round.
I can't imagine anyone using such a burdensome mechanic. It kind of boggles the mind, really. I'd say it's an easy bet that the authors never actually used this system in play. But anyway, the unique note on scale is at the end of the segmented movement table (Sup-III, p. 7):
Suggested Scale: 1":2'. Movements should be made simultaneously.