Nice price! But probably GF if it is the Service Six, GS is the Speed Six. Although some of the Service Six NYCPD guns were shipped in shippers marked Speed Six, the gun itself should letter as GF84-NYCPD.
triaxle:
If it is indeed a GS84 NYCPD, then it would be the first known. Be sure to confirm with us here on RF....will give everybody something more to look for!!
Chet15