This is attached to an old, wooden toolbox that I recently bought. The text etched into the lower part says "One and All". I'm curious if this is from some group or organization.
I was not familiar with horse brass, so thanks for that thread to pull on. It's as good a theory as any, tbh. I was personally thinking it was some religious thing, but I have no context at all other than it's tacked to a machinist's toolbox.