1st - I noticed this was your very first post - so, Welcome Aboard WWP! You didn't list your state (or country) in your profile. So, you might consider jumping over to Sub-Forum: Select Your Area.... for information (i.e., clubs, hunts, finds, legends, maps, etc.) directly related to your state (or country).
2nd - I moved ya from METAL DETECTING over to WHAT IS IT? for more exposure.
It's a civilian early 19th century "flower" button as they were called. It could be a little earlier, but this is the period they were very popular. I like it!