Phil Becker is a true master shaper who arguably has shaped the most boards in the industry. Maybe Terry Martin of Hobie has more, I’m not sure. Each has tens of thousands of boards under their belt. I remember reading somewhere that Becker has shaped over 100,00 boards(!)
Mangiagli has glassed many of his boards, including yours, so that’s what the other label is about.
Becker shaped for Rick Surfboards through the mid to late 70s before starting his own shop sometime around 1980. I’d estimate that yours is from the early 80s and is probably one of the early boards under his own label. The overall shape looks fairly typical of the period. The slots, although present on some much earlier boards, may have been a precursor to, or modification of the standard thruster which also came out right about that time.
He is still around and has one of the largest online surf businesses out there. If you can find a number penciled on it somewhere, maybe the shop can help you directly.