Last One

[ewymore]

Pretty sure this is US Navy...Albert NA112, probably around the WWI-WWII era, but whats throwing me off is no backmark and a screw shank (See pics). Its small...I would say cuff size.

 

[trikikiwi]

I'm guessing it is a hat/cap button.
Mike

Edit: A similar one described here as a cap button
http://tinyurl.com/nlkzfhe