Waltham Watchmakers Watch Mainspring Gauge

Waltham Watch Mainspring Gauge, marked Waltham, Resilient Mainsprings on the sides and Pat'd Jan.1.07 (1907) underneath.  Measures width and thickness far more accurately than a brass handheld gauge.  Tool is pretty good quality and still in completely functional condition given it's over 100 years old. Images do an adequate job of representing the item.