Welcome to Coins and Canada Seems like you have a project ahead of you. If you are looking at selling them, don’t be in a hurry until you know what you have. If you were to post a clear photo of both sides of a couple of your coins that you think might have value, someone here will be able to at lea...

I take it you are referring to a 1881 Canadian large cent.
A penny would be from the UK

Agree with Bill, there is no generic value.
Value would depend mainly on condition and variety.
It could be worth a couple of dollars or could be worth over $1000.00

Would you supply a complete photo of both sides. It looks like it may have been made for a piece of jewelry
but need complete photo to confirm.
One thing for sure, it didn’t look like that when the coin was struck.

I would contact them and see if they will replace it.
I know they will with coins.

Most likely some form of environmental toning.
It didn’t leave the mint looking like that.

The *AN series had over 1.5 million printed, the most of any replacement note.
Might get $20-25 each to the right buyer.

As the 1/2 cent was produced by mistake and the majority melted by the mint,
it would be virtually impossible to tell how many Specimen Proofs and business strikes
survived. As far as price, I would check the auctions and see what they are selling for.
I imagine yours would be in the 4 figure range.

It is not an error as it is on the die. Every coin struck with that die would have that on it.

Welcome to the forum.
The coin has been damaged making it only worth face value.
There is no way for that to have happened when the coin was struck.

Is this coin rare?

Not rare at all. There were over 4 Billion of the D mint alone produced.
It only has value in MS66 or higher.

It is always hard to grade a coin from a photo as lighting plays a big factor but I will say AU58.
There is some slight wear on the high spots. Perhaps someone else can give an opinion.

You failed to say where you are located.
I’m sure anyone interested would like to examine it before purchasing.
Also I assume that price is in Canadian dollars.

It looks more like an ink smear. An offset would show the face of the note in more detail.
Hard to say exactly without the bill in hand.

This as the title says is a Canadian Coin Forum
Not sure if anyone here can help. I know I can't.
Also a Doubled Die is not an error, it is a variety.

Yes, please more information. Most collectors specialize in certain coins so we need to
know what you are selling.