My avatar is a tool check from the Ford Motor Company River Rouge Complex Ford Motor Company here:
http://www.thehenryford.org/rouge/index.aspxWikipedia here:
http://en.wikipedia.org/wiki/Ford_R...ouge_ComplexDerived from 19th century carriage-makers, the automotive industry has always depended on outside contractors, with nameplates being assembly work. Companies would stamp their own sheet metal bodies, machine their own engines and transmissions, but still buy seats, seat covers, and all the rest from outside suppliers. (In Japan, Honda got its start making piston rings for Toyota.) Henry Ford launched "The Rouge" as an experiment in integrated manufacturing. His own ore boats delivered iron and coal to his steel mill.
The tool "crib" is common to manufacturing and construction. Tool checks were issued to workers so that they could borrow tools from the crib. The check was placed where the tool went. If the tool was not returned, they knew who had it.
Tool checks are a form of exonumia on two grounds. First, of course, they are coin-like in being stamped in metal. Also, they stand for a fiduciary agreement to safeguard the tool borrowed and return it in good order.
I lived in Michigan for many years and these are both common and pricy. Everyone has them; everyone wants them. Also, technically, they were not to be taken from the plant after separation from the company; but clearly, they were.
I have other tool checks from different firms in different industries. They are at once interesting on their own merits, and also not so hotly pursued by Michigan coin collectors who used to work in automotive manufacturing.

