Risers were A (shortest, for hunting), B, and C (longest, for target shooters).
Limbs were #1 (shortest and the norm), #2 and #3.
An A riser w/ #1 limbs is A.M.O. 56", a B is 60". A C w/ #3 limbs will make a 70" bow
William
(removed wrong information corrected by oldskoolarcher)