Here is a "MINT CONDITION" Hamilton 4992B "GCT" black face 24 hour dial, military pocket watch in excellent working condition!  22 jewels, Adj. 6 Pos/Temp, base metal Keystone case #7592614.  Back of case is inscribed "AN5740, Mfr's Part No. 4992B, Contact No. W535ac-28072, Serial No. 42-26957, Hamilton Watch Co.", all of which defines the military contract under which these watches were produced.  Back of 2" diameter 16 size case unscrews to reveal a shiney, like new movement, that still runs like a top!  Very clean, no wear at all, appears to have never been used.  Serial number 4C58550, makes this watch c1940.