B-100 Preamplifier
The B-100 was the first product to released by Boss. It went to market 1974 and consisted of a contact microphone for acoustic guitars and the preamp unit seen in the picture. The product shipped in a wooden box where the Boss logo was displayed for the first time ever. The battery driven preamp unit has a belt clip on the back. There was also a model called BPA-200 available that featured an additonal BALANCE control. Check out discofreq's pages for pictures and more information on this unit.
Note that this product is not made by Roland corp. The product is created by Beckmen Musical Instruments in the US. In the 70s, Thomas Beckmen and Roland corp, Japan became joint owners of Roland US. Roland corp acquired the Boss brand through this business deal and has used it ever since. The box has the inscription "A product of Beckmen Musical Instruments Inc" while the preamp unit has "Made in U.S.A" written below the non standard Boss logo.
Picture courtesy of Bobby's on Broadway