Manufactured by:Rinck McIlwaine Company. I can test valve springs for pressure at installed spring height, and cam-open position. The arm can be locked to test spring fade over time. Tested....it works perfect ! The heavy cast iron base keeps it put when testing springs. It looks to be made in the 1930s or 40s??? I'll clean it up and paint a sturdy cast gray shop color . . . Vintage tools. Made in USA. Restoring vintage engines with vintage equipment.