Bartell of California 1964-1969 Founded by Paul Barth (Magnatone, worked for Rickenbacker, and built Black Widows for Acoustic in 1972).  Instruments built in Riverside, California, USA 1964-1969.  Bartell of California appears on label inside Hohner fretless basses.

The best resource for Bartell is the Unofficial Bartell Fan Site

http://www.allthetransients.com/subdomains/blackwidow/story.html

Image eBay:Bartell of California bass guitar