A friend has asked me if I can find out anything about the value of this ring. (Not a metal detecting find.)

The ring is gold but the markings on the inside have worn off. The initials are B of L F & E which stands for the Brotherhood of Locomotive Firemen & Enginemen. My friend thinks it is from the 1909-1930 era.

I found a couple of similar rings online but none exactly like this one.

Does anyone know of a resource that could help with the value of this ring?