The 1838-O Capped Bust Half Dollar was the first branch mint half dollar and is the lowest mintage of all CBHs with a reported mintage of 20 coins. In Fine condition this coin Grey Sheets at $160,000. The 1838 Philadelphia CBH had a mintage of 3,546,000 and in Fine condition Grey Sheets at $65. The incentive to alter a genuine 1838 CBH to an 1838-O has existed for a long time (probably since 1893 when coin collectors first took notice of mintmarks). I have an example of such an altered coin. It is a poor fake that should not fool anyone (especially someone willing to pluck down big bucks for a great rarity). Someone created the 'O' mintmark on the obverse of the coin by carving down into the coin and leaving a "raised" mintmark that any beginning collector could spot. OK, perhaps whoever created this fake never intended to fool anyone. Maybe he just wanted to fill a hole in his coin folder. And he did not destroy an especially valuable coin; the host coin already had a hole that has been poorly repaired. It is still an interesting piece. Enjoy!
besides the crudely altered mint mark the coin is not that bad. I would gladly add it to my collection..
When I get my a couple of more pieces for my photography set-up I'll take a photo that shows the alteration a little better.
The toning on that coin is also quite lovely! You can almost see more detail then actually exists due to the contrast it provides. ~Droid