I was a carhop at a sonic drive-in in a bad part of Tulsa oklahoma and a girl gave me this 1979 Kennedy half dollar. I was just starting to collect coins then and am still a beginner. It was so shiny and new looking I hung on to it. When I got home and took a look at it I saw that it had 1960 stamped on the front left side and 1980 on the front right side. The quality of the coin must be MS-65 or 63 I would guess, but It appears to me as though this is out of some kind of commemorative proof set... I just don't know and haven't been able to find any info about it at all, so here are some pics

Front:

(Click for full size)

Back:

(click for full size)

If you'll notice, on the back picture, the corner of the D on United is flattened a bit from whoever stamped the front. The E in America is also flattened a bit, but in this scanned picture you can't really tell. I was amazed at how flat it looks in real life as compared to the scanned image.

So my guess is it's from a commemorative proof set of some kind, hence the stamp. I am also guessing it's worth less since it's stamped like that and not in a set...Anyone else have an idea of where it came from or how the stamp affects its value?

IMO the stamp was done privately to commemorate some anniversary, and was probably given out as a favor. The coin itself is probably AU, as there are signs of it being handled.

With or without the stamp, the coin is relatively common, and is worth 50 cents. But the stamp makes it a bit more interesting, and to the right person, might be worth more!

Those dates were placed on the coin after minting. Notice how they correspond with the flat points on the reverse that you mention. The stamped dates would actually decrease the value (if it were a particularly valuable half) as it would be considered damage - but it makes for an interesting piece. It's commemerating something, but not any kind of US Mint commemorative.

I should invent an interesting story for it when people see it in my collection...Thanks for the info!