Currently working and was tested over a 19 hour period and kept poor time, lost approx 10 minutes, ticking a lot slower than it should. It will need a service or repair to keep absolute perfect time. The skeleton back case is 51.4mm in diameter. 1907 Waltham, Grade P S Bartlett, Model 1899, 17J, 16S, stem set, stem wind, double sunken dial with date serial number 16051820. Dial has a small loss to edge between 1 & 2, slightly stiff to wind.