I believe 'Stiffwrists' called it. It looks like a "tool tag" or "tool check" used to keep track of items given to workers. The font of the "30" has a 1920s to 1940s look to it. The local library near where it was found might be able to help you identify the "BFM Co." using old telephone or business directories like 'Polks Directory'. You may be able to just email them your research request via their website.