There is indeed a "methodology" to doing so... as one of my associates has proven time and again. I don't know how he goes about "dating" watches in general, but movements ALONE are inadequate, for doing so... for the reasons I pointed out, above, etc. Incidentally, it would appear the "inaccurate" production datings mainly relate to using movement symbology, as aforementioned? However, the inaccuracies I was referring to all seem to be around then years off, either direction... which is intriguing, I think? (Cases in point: 1951, vs '41, "Knicherbocker," 1938 vs. 48, "Rite Angle," etc.) I already corrected a guy on one 1940 vs. '32 President "F" model... which he amended, thereafter... And of course the only way to avoid "miss dating," etc., in general is to police it, which I doubt is very realistic to Stephen or anyone else, to keep up with???
But the bottom line on production and release dates, model IDs, etc. is eventually finding more comparitive data for a refined "double check" analysis... Gruen, for instance was ultimately sold (like most) and all the records were discarded, thereafter!? However... at least most 1940ish + models were stamped inside the caseback with the movement &/or model numerics. (In: 2, 3 or 4 digits, or XXX - YYY +/- speak.) Bulova however only used watch serials and movement serial and date markings. So unless one has a vintage illustration or the like, then it comes down to serial no. production runs/dates... which DO exist somewhere, I suspect??? I'll also look into it. Has anyone perused the various watchmaker guilds and the like, online? That's where I got most of the Hamilton data to add around 200 models (and since added photo IDs) on eBay...
BEST :-) William