You were right... It is very likely 1075.
C:*0.70-0.80; Mn:*0.40-0.70; P:*0.030;
S:*0.050; Si:*?;
Standard: AISI (US)
Notes:
Relatively simple carbon steel. Can produce pretty decent results when heat treated properly, Several knife manufacturers use it in their budget knives, including Boker folders.
Cross-References:
Standard:
AFNOR - C72D
AFNOR - FM72
AFNOR - XC75
BS - 060A78*
BS - 070A78
DIN - C72D
DIN - C75
DIN - CK75
DIN - D73-3
DIN - D75-2
DIN - D78-2*
DIN - D78-3*
EN - C70E
EN - C70G
EN - DNH7
GB - #75
GB - 8MnSi
GOST - 75
JIS - S75C
JIS - SWRH77*
JUS - C.1832
JUS - C.1837*
SIS - 1774
UNI - C75
UNS - G10750
W-Nr - 1.0605
W-Nr - 1.0617
W-Nr - 1.0620
W-Nr - 1.1248
W-Nr - 1.1252
W-Nr - 1.1253
Proprietary:
Bonpertuis - DNH75
Nisshin - NK11
* - Maker(s) list the alloy as similar or a replacement for alloys in this group.