...and the Wide Ring PO-CA thru PO-CZ; circa 1908-1938. Your example seems to be a Narrow Ring.

Though the letter "H" on the chip you illustrate is the same in both PO-C and PO-G codes, the "B" in the Wide Ring series (PO-CB is nowhere like the B on the chip... I have no reference to that style B and it could very well have been made to match some B, somewhere, but where, and who really cares ?

Interesting chip if it's an inlaid; haveing two different style letters.

JB