indiskret

arms of the Duchy of Cornwall

That's it! Thank you very much!

They also make fantastic insulated mugs. My coffee stays hot for hours in that thing

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.