This post is in response to a query on Letpress:
Vandercook first issued serial numbers on presses in 1914. Until about 1925 they were located directly on the press bed at the right end midway between the lock up pins. It may be hidden by a removable bed plate and/or rust and oxided ink.
This number appears on a 1932 Single Truss No. 1 owned by John Horn.