Most of the 5946 NYPD had conventional S/N marking, but when SW moved 3rd Gen Production to Houlton, ME circa 2010, the markings changed especially in the Holton pistols with UCx prefixes. Most of the UCx Houlton pistols had s/n on right side in indented ovals. When SW moved 3rd gen production back to Springfield, circa 2016, the indented right S/N was retained. It appears there were residuals with Houlton markings assembled in Springfield - I have a 5946 NYPD verified with frame marked Springfield and slide marked Houlton.
I would assume a similar sequence for the 3914DAO. As far as I know the 3914DAO were made for NYPD, but at least in the last days, a significant number were surplused. There may have been other buyers before that as there seem to be a lot out there.
I have documented 40 3914DAO pistols including 24 with original boxes - all product code 103922 with all but the MSFs (1998) either Spec Ord or SW dated between 2000-2017.
Earliest I know of is my MSF41xx product code 103922 (6/1998 per SW) marked Springfield with model & S/N conventionally marked on left. They progressed thru the VJx groupings circa 2003 and the BAx, BDx, BEx and BJx circa 2006-2008 all with Springfield markings and conventional left side S/N markings. They appear to have progressed thru the UBZ, and UCF (circa 2009-2011) with Springfield markings but now with 3 lines = location, model, & s/n left (as opposed to previous model & s/n only in 2 lines in same left side location).
The first Houlton 3914DAO I have observed is a UCS74xx circa 2012 with indented s/n on right. UCT, UCU, UCV, and UCW pistols have been observed with Houlton markings and indented Right S/N (circa 2013-2014). At least in the UCV and UCW series, the Houlton 5946 and 3914DAO pistols were intermixed.
Beginning in 2015, the 3014DAO pistols were marked Springfield, Ma including some in the UCW series and all the UCZ and it appears most if not all of the 2015 and subsequent production were surplused. These maintained the right indented S/N for the most part, but on the UCZ pistols they were no longer indented. I have a 3914DAO with right S/N UCZ62xx product code 103922 but without indentation. This is the newest 3914DAO I have observed with SW dating its production as 10/2017. It appears to be from a group of 83 similar UCZ series 3914DAO pistols shipped to Lipseys in Baton Rouge, La.
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