Master krafter Armour and co.

[rustyfordgarage]

Master Krafter Armour & Co. Chicago
Spring loaded tension gauge?  The shoe on the end has a spring as well as a heavy spring in the middle tube. Also a brass pulley on the end by the shoe.  First thought was a belt tension gauge. But with the Armour name maybe a meat saw tension gauge. But my guessing is usually off on the things I find, so what is it really?