Any Ideas?

[cornspike]

Eagle with crossed sword and a key, has screw on back, a little bigger than a quarter. Round Tin about 10" around, any idea what it was used for or years? Thanks for looking

 

[nhbenz]

The eagle thingy is a collar disc from the quartermaster corps; Quartermaster Corps (United States Army) - Wikipedia, the free encyclopedia
WWII era I believe (see middle of link, unclassified variety): http://hglanham.tripod.com/metalinsignia/collardisk1.html

 

[cornspike]

The eagle thingy is a collar disc from the quartermaster corps; Quartermaster Corps (United States Army) - Wikipedia, the free encyclopedia
WWII era I believe (see middle of link, unclassified variety): Dating Metallic Insignia: Collar Disks

NICE!!! Thanks....

 

[Lafitte Deux]

The disc looks like an old car headlight retaining ring.