Please help to know rare or common Belgian coin. [gelöst]

I found error coins in my collection with fully covered “N” in UNION word.  It is common not rare coins, but I never met it type of error before. May be some Belgian collector explain what is it.  Thanks.

It looks like someone made modifications to it, maybe to make some sort of button pin? There seems to be a filled up hole at 180 degrees from the extra metal.

Dear DuikerTS. Sorry it's looks as mint error, I can't remove metal covered “N” in union. Thanks for reply.

Also if you carefully looks it coins, you found 2 line of mint error near L and star. It is also made for button???

Rus-1975

Also if you carefully looks it coins, you found 2 line of mint error near L and star. It is also made for button???

The line near the L and star is a die crack, which is indeed a mint error.

With respect to the rectangular surplus metal and the circular damage opposite of it, I side with DuikerTS, that they are the remains of post mint welding. Probably the coin was first made into a button or brooch and later, the attachments were removed again. A lot can happen to a coin in 163 years.

Thanks all. Will sent to button coins.