This is the original logo die stamp used to make the "Genuine Hummingbird" logo. The logo is etched in reverse on the plate, and the plate was pressed hard against the wood to impress the logo. A one-of-a-kind Hummingbird collectible. This particular plate shows some wear, and the machining suggests less logo depth.
This die stamp appeared on some of the more limited releases, like the Dale Myrberg and Dennis McBride custom yo-yos.