I opened up my '76 Music Man Stingray 1...

[velevg]

...and found this:

8-18-76 (obviously date of neck)
8-26-76 (date of body)
MJR
JPG

Does anybody know what MJR and JPG could stand for? I have no idea!

 

[GWDavis28]

They could be the intials of the builder. Not 100% sure though.

Glenn |B)

 

[the24thfret]

Maybe if you post the same question on the bass side of the forums someone would know... I'm not sure myself.

 

[John C]

I suspect those were the initials of the builders in Leo Fender's CLF Research factory (now the G&L factory); EB wouldn't have any details since the StingRay I guitars were from the Leo Fender era. You might also post on the G&L forum (guitarsbyleo.com) as there are some fans of the original MM and Leo-era G&Ls over there who might be more connected with who was in the factory back then.

EB bought MM from bankruptcy in 1984; MM had only made amps and basses after they ended their relationship with Mr. Fender (shortly after he converted his shop to G&L designs and production) circa 1980/81. It seems like MM only produced basses and amps in 1982/83.