Nice find there Nes. Congrats on your 1'st military piece!
Pretty sure I joined the club a couple months ago, but it's super toasted. Has the same field of dots as yours does, and the reverse side has what I believe is a wire shank (rookie guess). Tried ID'ing it online, but button sites are scarce. Maybe Santa will bring an Alphaeus Albert book.
Maybe an inch in diameter. Think it's right-side up in the pic.