Is it possible this 1940 wheat penny could be a mis-stamped penny. It has no mint mark and it has a ridge sort of like a seam on the rim. There is a small amount of copper showing through on the rim.

Are you sure its silver? Or are you describing color? They made zinc war pennies in that year.

Ref:

Values of Wheat Pennies

LEEANN55- The 1940 wheat penny you have is from what you say,what is called a { PLANCHET; } Which in 1943 ,there were some specimens struckion BRONZEPLANCHETS, by mistake and there are a few known to exist;; ;; in G-4 a 1940 penny its value is .15 cents;; ONE IN GRADE AU-50 value is {$2.00} :: I hope this has answered your questions, if not come back and holler on this post;;; Have a great day and GOD BLESS:: F.B.E.