A while back Wes H. sold a couple of the nice Blue Sunoco PPP that have the diamond shape and S and O protrude below. He mentions they were marked P&M on the bottom. P&M appears to be a sign maker from Canada (1930-1950).

Any obvious ways to tell these style PPP are not repro? size? other marks from other sign co.'s like the P&M mentioned above? grommet holes?

Thx.