I'm not sure if this went, so apologies for double posting.
I've been keeping records of the GSTPs that I've seen either personally or on the web (ebay, etc) and the results so far are:-
"Buren" H (5)
"Cortebert" T (3)
"Cyma" T, H, M, /|\S (21)
"Damas" GS/TP plus 5 or 6 digits (2)
"Doxa" H, 6-digits (5)
"Elgin" A, G, 6 digits (7)
"Enicar" (movement marked only) 6 digits (1)
"Frenca" Q, /|\S (3)
"Grana" J (1)
"Helvetia" P, 6 digits (23)
"Jaeger le Coultre" F, L, M, P, 6 digits, /|\S (32)
"Leonidas" J, L, N, T, /|\S, 6 digits (14)
"Moeris" M, P, 6 digits (13)
"Omega" F, Q, Y (17)
"Recta" F, M (3)
"Tissot" F (1)
"Waltham" E, 5 digits (5)
(i) /|\S refers to an S stamped immediately below the broad arrow (I've also seen an /|\F on a stopwatch);
(ii) Similar letter prefixes are marked identically across manufacturers eg Recta and Jaeger le Coultre with 'F' markings have the same (diestamped) marks, with similar arrows, or Buren and Doxa H-marked watches.
(iii) Sometimes marked GS/TP, or G.S.T.P, with the arrow above or below
(iv) the XX marking seems in some cases to be a later addition, in others it seems to form part of the offset of the number (and hence was done at the same time as the rest of the marking). Does it indicate XX Corps in this case?
(v) Some of the markings are die-stamped, some machine engraved (although some of the engraved marks have a die-struck broad arrow).
My theory is that batches of watches of different manufacturers were marked in different places by the army, so the Rectas and JLCs referred to above might have been received together, etc. - anyone else any info on this?
Marvin - if you want to email me offline, I can provide more info and scans, etc.