http://cgi.ebay.com/1921-D-MORGAN-DOLLAR-CERTIFIED-PCGS-MS64_W0QQitemZ120496860725QQcmdZViewItemQQptZCoins_US_Individual?hash=item1c0e2c2e35
This is in PCGS plastic. Not eating words or hat on this basis. Besides, you said "thousands," and this one didn't go for anywhere near!
1942 half penny Sounds to me like you have a 1942 half penny from Great Britain. Georgivs is the Latin name for George (George the Sixth in this case). If the coin does not have a recognizable country name, it is in all likelihood from Great Britain.
This is my last word on the subject. My only point was you can't tell someone their coin is basically worthless without seeing it.
But you can tell them the truth - the odds are very high that it isn't worth much of a premium over melt - instead of giving them false hopes that they have hit the jackpot!