It is a Dan Armstrong London bass, short scale. Dan Armstrong moved to England in the '70s and came out with this wooden series of guitars and basses that were modeled after his Ampeg plexiglass creations. More info and pics here: http://www.danarmstrong.org/londonbass.html
The Travis Bean didn't appear until the Tatoo You album/tour.
The Steinbergers come in after that, in '83 and then to this day. First and L2 then to the XM's when they came to be.