The 1951 Brewer Sewing Supplies Company catalog had three versions of sewing machine “Repair Jacks” listed for holding sewing machines to work on them. The “Wedge Lock” #1205 ($25.90), the “Roemer” #1206 ($15.00), and the “Boco” #1207 ($25.90). The Boco was “The Sewing Machine Vise Combining All Important Features Required by the Mechanics”.
I wish Brewer still carried them.....
The photo is mine, but the catalog contents are copyright 1951 by Brewer Sewing Supplies Company.
CD in Oklahoma