My roommate has a red 8-string bass he bought about 30 years ago from a music shop in Seattle. The head is from an Epiphone 12-string guitar with 4 of the peg holes filled in. The back of the head has a serial number stamped in: "521564". The body is a double cut with a single pick up. It's just a flat piece of wood with square edges. On the back of the join plate is a different serial number, "L770100 Made in Japan". Any ideas?