I've seen one of these before but I can't remember what it is! It looks like a piece might have been broken off at the center like it covered the hole. If possible can you date the item.
Musical instrument reed, likely from an accordion or possibly a concertina.
These brass reeds can date from the mid-1800's, on through the 20th Century. There are subtle differences in shape and style, that can sometimes be helpful in pinpointing the exact instrument and time frame. Each instrument had a number of these in graduating size, to obtain the various musical notes.