The US1, I almost bought one as a teen in a pawn shop but my mom said no!Very cool, from the era of the Charvel Gibson collaboration ( late 80's)... I haven't seen a Mach 2 in a long time. If memory serves me correctly they were known as a U2 for the first few years of production and then switched over to the Mach 2 for the last couple. The body is basswood , unlike the US 1 which was "Chromyte" or balsa wood core with maple caps. Great score!