These types of vibrola tailpieces were used on many Gibson® guitars in the mid-late 1960's.
The short Gibson® style vibrato tailpiece includes the vibrola mechanism and arm with the flat style mount.
Note that these are replications of the OEM equipment used on Gibson® guitars such as the Firebird®, SG® Jr, SG® Special, SG® Custom, Melody Maker®, and '67 Flying V® Reissues.