Vintage Sterling / Enamel BPOE (Elks) locket

I picked this up this past weekend at a local antiques show. It's marked Marathon/sterling The emblem is quite detailed, with the Elks "clock" symbol clearly readable under a magnifying glass. It may be a stamp holder, it has a small clip on the inside. There is a plate for initials, but it's not engraved. I also have a compact marked marathon, and both seem to be high quality. Thanks for looking!