Leo-era Musica Man only made 2 models - the Sting Ray and the Sabre - and both guitars had 2 humbucking pickups.
When you see a "Sting Ray I" and a "Sting Ray II" the "I" means it had a 12" radius neck while a "II" had a 7.5" radius neck. However, I could have the "I" and "II" reversed.