This is a George A. Wilson Match .45 ACP. It is one of three hand built by George Wilson, who was a designer for High Standard and a competitive bullseye pistol shooter. He designed this pistol for his own competition use in 1959, patenting the design in 1961.
Please see a full video takedown and review on ForgottonWeapons.com for a lot more detail on this pistol.
My research does not show the George A. Wilson that worked for High Standard to be the George A. Wilson that made the 3 target pistols. I own Wilson pistols 2 and 3, the matched set, though there are several important differences in the two. Also I have the wooden model of number one and the production drawings, also letters from Mr. Wilson to other people. Also have two articles about the pistols at the time and no mention at all of High Standard……….our Wilson worked in a different industry.