Encircled "M" = State of Michigan.
I don't have a perfin catalog, but I understand there are a number of varieties of this sort of stamp that was in use for decades. Someone with a catalog can identify the usage and type.
In fact, referring to this old thread the stamp shown looks similar to mine, which is identified as:
Quote:
Circle(M) is State of Michigan, perfin pattern M9, value $.15 - there is a closely related perfin pattern M8.7 which has two distinct serifs on the base of the M, as opposed to pattern M9 which makes it look almost like a single line under the M.
https://goscf.com/t/16797
Posted 09/14/2014 9:30 pm
