Looks like very late die stage with a die chip in the date? I'm guessing as if it were a poll. Someone will chime in the actual answer in a minute. For recognized varieties there are a couple of websites with pictures to match your coin to, to hang a preposition. Probably also one or two devoted just to this type. Google is your friend, unless it recommends Etsy.
These were among the 1st coins the mint struck using the 75-25 Copper-Nickel alloy, which is a lot harder than the 88-12 used for the FE and IH cents. The planchets are thicker than the 3 cent nickles... net-net the mint had a lot of problems with cracking dies. BTW: It's not considered an error nor even a variety. Same with die chips. And clashes (unless you have a good PR department like the Bugs Bunny Franklins)
Havent posted in a while, my mother passed away and things have been crazy and difficult this year. (For everyone I'm sure) . I have another 3 cent Nickel question if someone has a few minutes. I realize the 1865 Proof is somewhat rare, but I recently came across this and was wondering if it is a proof and how to distinguish the difference on this particular coin. If anyone is familiar with the 3CN and has a resource, it would be helpful. Thanks.