9x19mm 'S' headstamp

I’m assuming that the ‘S’ in this headstamp indicates subsonic but could somebody confirm this please?

this was a military contract for the U.S. - probably Navy Seals. It is a subsonic load. Subsequent rounds used an “L” designation for subsonic, which some confuse as standing for “Luger.” They have the same headstamp, but dated 91 (and perhaps other dates) and a “L” where the “S” is on your headstamp.

I will have my Forum “pard” Joe post pictures of my boxes for both types when he has the time.

Thank you John.

TOP BOX: 1989 for the “S” headstamp.
BOTTOM BOX: 1991 for the “L” headstamp

Headstamps of the two Federal Subsonic rounds, from 1989 and 1991, showing the different letters used for identification as a subsonic cartridge.

Collection of John Moss