Currently working and was tested over a 21 hour period and lost approx 30 seconds. It may need a service to keep absolute perfect time and is sold as is. The base metal case is 52.4mm in diameter. 1910 Hamilton, Grade 940, Model 1, 21J, 18S, lever set, stem wind, railroad grade, 5 adjusts, double roller, double sunken dial, gold screw set, motor barrel with date serial number 662665. Dial has a crack between 2 & 3.