I suspected *all* the Izhevsks generally had different font width ratios, but I never really was sure enough to really make that call. The receiver cover S/N thread made me look into them more and now that I've got the Russians all catalogued nicely in the current S/N spreadsheet, it's a breeze to look at every single Izhevsk and then break them down further into as-issued and light furbs to see what the markings truly say. The 4's are extremely different too.
I should make a thread showing examples of the digits from various years, would help in identifying orphans w/o matching receiver covers and stocks.