I'm not sure what Union Cutlery called it, but when Union made this for the B.S.A. in the period 1937-1939 (or 1940), B.S.A. called it the Model No. 1555.
And it is stainless.
Thomas, I found this in Joseph Kerrs (600 Scout Knives), Union Cutlerys Ka-Bar 1555
SEA SCOUTS UNDER KA-BAR TRADEMARK
(Information duplicated in Chapter 7 on Official Explorer Knives.)
KAB11BS 4.00" (8.00" overall) 1-Blade Ka-Bar Sheath Knife/Marlinspike (275 P)
The 1939 catalog lists broad 8.0" sheath knife (BSA#1555) with a 5.50" marlinspike in a single
sheath for Sea Scouts. Named the "Voyageur" model. MB(M): OFFICIAL<>KNIFE/BOY<FC>SCOUTS/OF<>
AMERICA/<blank line>/VOYAGEUR. Sheepfoot blade, cocobola wood handle with 3 rivets, hole in
handle for thong. Apparently only made 1937 to 1939. SHEATH: 9-rivet, two section, wide design,
loop at top, BSA stamp (wording known). Points to observer's right. Judging from non-BSA models
the BSA MB(M) may have CARBON KA-BAR CHROME. The inspected non-BSA sheath was 5-rivet with KA-BAR
stamp on 7.50"x2.50" leather with 3.75" belt loop opening. [H3740]
KAB12BS 4.00" (8.00?" overall) 1-Blade Ka-Bar Sheath Knife/Marlinspike (250 P)
A replacement model with drop-point became BSA#1555 with a 5.50" marlinspike in a single sheath
for Sea Scouts. Named the "Voyageur" model. Cocobola wood handle. Apparently made 1940 to 1942,
in 1941 catalog. SHEATH: Two section, slim design, BSA stamp (wording unknown). Probably 4-rivet,
points to observer's right. [H4042]
If I'm reading the above correctly it looks like your's is the earlier version.