It is definitely a Williams cabinet.
I have a Robotron cabinet that I restored, was a Capcom game when I got it:
http://forum.arcadecontrols.com/index.php?topic=63639.0This mystery cab is identical in dimensions and hardware scheme as my Robotron. It has the same type of coin box with the tubes sticking out of it, same coin doors, same handle in the back, same rear doors, same bezel, same Williams monitor shelf, same construction throughout. The only exception is that the bottom front part of the mystery cab is made from MDF, while the rest of the cabinet is plywood. The Robotron bottom front is plywood.
I actually got this cab for spare parts to my Robotron restoration.
They had about 100+ dead cabs at this auction, and about 40% or them were Williams cabs... Robotrons, Jousts, Defenders, Stargates, etc... All but 2 or 3 had wood-grain formica sides... such a shame I could not take them all... They also had lots of other cabs with wood-grain formica... not just Williams cabs, but many other types. I got a Track and Field cab with the same wood-grain formica that same day.
From what I gather, most or all of these converted cabs came from the same op somewhere in Texas... most had the same generic CPO, marquee scheme, tax tags, and siding... must have been a huge operation.