The "experts" at many if not most coin shops wouldn't know a error coin if it bit them. That is other than the blatantly obvious such as off-centers or the major Doubled Dies that are in the Redbook (And they can't recognize some of those either.) If the dealer doesn't specialize in errors and/or varieties, they will probably know less than several of the specialists here.
I have this same exact 1976d penny and in very good condition and yet it looks gold. I matched it to some of my jewelry and it looks like 22k gold in color. I'm not saying this is what it is as im also wanting to know. I've had this coin for so many years and forgot about it until I recently pulled out my old unique change. If you find out anything plz let me know. edited .... thnx For your own protection, do not post personal info on the forum.
I'm sitting here right now looking through 3000 pennies, and ALL the 1977's including one 1976 is brass colored, VERY brass looking! I have to wonder.