yes agreed CanAm all the '75 RM125S, 125M and the RM100A tanks were steel.
The RM100A uses the same steel tank as a 125M and the '74 TM125.
RM100B uses the same alloy tank as the RM125A and B.
only the '76/'77 RM125 and the '77 RM100 (as well as RM250/370A/B) had alloy tanks