That is the gun that just sold on GunBroker and I suspect it is indeed a GS83-NYCPD since it came out of Merrick, NY. Barrel is 3" as stated in the ad. Same seller had a GF84-NYCPD (Service Six) that sold the prior week (the Speed Six was listed then too but closed with no bid). Both guns were duty arms for NYPD and the star was stamped by the NYPD armorer after inspection.
Glad someone here got it. When you know the SN, please post it, or let me or chet15 know. There are only a half dozen of so of each model known so far to collectors. There is a thread on here from a few months ago that discusses these in detail.
Here is a Speed Six w/letter:
Here is the Service Six, shipper says Speed Six but is numbered to gun:
Here's another star pic: