The listing says 1973, but that's incorrect. (The Mockingbird design wasn't introduced until 1976). it is, however, a very early Mockingbird based on the serial number, full Koa body with no maple stingers, and the two (instead of 3) coil tap/phase switches. The XLR is not stock either:
http://cgi.ebay.com/1973-Left-handed-BC ... 35a4837337FYI, I just bought a '77 BC Rich Eagle Bass from Tom Tyner at
http://www.leftyloserguitars.com. (That's mine on the home page). He's got tons of lefties, especially BC Riches, including a lefty Wave bass (I've never seen another). Tom's a good guy and his prices are reasonable/negotiable.