This is a 10 karat gold Oldsmobile 15 year loyal service pin which by the winged spur logo dates between 1919 to 1940. It measures 3/5 x 3/5 of an inch, weighs 2.81 grams and is in excellent condition.
The back is hallmarked “B.M.&Co. Cinti. O 10K” which I believe refers to the Gordon B Miller Company based in Cincinnati Ohio, which was the oldest recognition products company in the US until it was bought out by Jostens in the 1990s.