Thanks. My 5946 has the S/N on the right side of the frame, just like my 3914DAO. I thought that was a NYPD feature. I'll have to check the 3914DAO , but my recollection is that it would not fire with the magazine removed.
The RIGHT side s/n were not unique to NYPD pistols, nor were all NYPD pistols configured with RIGHT side s/n markings.
The majority of the NYPD 5946 pistols I can identify are Product Code 108569 circa 1994-1999 in the Vxx groupings (with a few TDx c1999 and at least one KNC c1998) from Springfield, MA with conventional LEFT side s/n.
5946, 3914DAO, and 3914TSW pistols up thru UCF25xx were marked Springfield, Ma with original LEFT side s/n markings.
There were also a few conventionally marked (s/n on LEFT) 5946 pistols in the Vxx s/n prefix (VJN9xxx, VZE4xxx, etc.) marked HOULTON, ME.
I believe the S/N on RIGHT side began during the Houlton, ME produced pistols (2010-2015?). The indented s/n came about about the same time (lowest s/n I have observed with indented s/n on right were the Melonite WVSP 4566TSW UCK5xxx circa 2011 - also 5946 UCK8xxx). Also observed UCK, UCS, UCT, UCU, UCV, UCW.
The later HOULTON, Me marked pistols with INDENTED RIGHT side s/n continued thru the UCW series with at least a few UCY - but most of the UCY series seem to be 5946 with INDENTED RIGHT side s/n but now marked SPRINGFIELD, Ma circa 2015-2016.
But there were also conventionally applied (NOT INDENTED) s/n markings on the RIGHT side in the UCZ series - in fact all the UCZ pistols seem to be so marked. I have a very late 3914DAO UCZ62xx marked Springfield, Ma circa 2015-2017 with box end marked "NYPD".
And there are some odd pistols with Frame marked Springfield and Slide marked Houlton and vice-versa.
One might speculate that residual unassembled parts were transferred from Springfield to Houlton in the beginning (c2010) and from Houlton back to Springfield (c2016). One could also speculate that Houlton used a different source for frames with the indented s/n and Springfield went back to their original source when production was moved back from Houlton.