I've had this thing for about 40 years. It's a pair of crossed cannon barrels over the number 73. It appears to be bronze, not brass, and is in very good shape with no dents or bings and only a small amount of wear through the patina finish. It measures 1 7/8" wide by 1 1/2" high. Claspo is a swinging wire pin and a wire hook, both of the same metal as the device.
It's been in a box with my cuff links and tie pins and bars, a box that hasn't been opened in 25 years.
Thanks for any help I might get.