I believe the pusher evolution followed a back-and-forth turn on the Speedy Pro premoons:
[a] early 105.012s, up through and including the -65s that had screw-fit pushers, featured taller pushers (5mm x 3.5mm tall)
b] 105.012-66s had press-fit pushers that were short (5mm x 3mm)
[c] 145.012's returned to screw-in, taller pushers (5mm x 3.5mm)
In my observations, the 105.012's that had the cases with vertical facets on the lugs unique to 105.012-66's (and possibly late 105.012-65s), came with the press-fit, shorter pushers. The early 105.012 cases did not have vertical facets on the lugs, and these cases came with screw-in pushers. Starting with the 145.012-67, the vertical facets again disappeared, and the taller screw-in pushers reappeared.
As has been discussed elsewhere, Omega qualified multiple subcontractors to manufacture or supply their watch parts. I believe that not coincidentally, early 105.012 cases (on their caseback insides) were all marked with the HF hallmark, indicating they were manufactured by Huguenin Frères. The late 105.012 cases (on their caseback insides) were all marked with the CB hallmark, indicating they were manufactured by Centrale Boîtes. All 145.012-67 cases I've seen were again marked HF - so this may explain why the vertical facets and shorter, press-fit pushers appeared briefly.
This next paragraph is speculation, but I'm postulating the vertical facets on the lugs were an artifact of the machining process (perhaps even the individual machinist's technique, if they were handmade) CB used to make the case. And, it's probably a safe assumption that CB had a supplier from whom they sourced their pushers. In doing so, they selected shorter, press-fit pushers that matched the case (which they built for a press-fit, rather than being bored and tapped for a threaded pusher). As for why CB selected a press-fit pusher. . .maybe it was a supply constraint; or, maybe Omega's specifications were broader - perhaps giving a requirement for min/max pusher travel to ensure the movement is appropriately engaged by the pusher when depressed, a max pusher height to conform to enveloping watch dimensions, and perhaps minimum pusher diameter and actuation forces if user ergonomics were a consideration back then - but beyond this, Omega's subcontractor (CB) was free to meet the specifications in any way they saw most efficient and appropriate to do so.
cheers,
Mark
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