Different styles, sizes and eras. First half of the 60's for the E 2638 on the right, End of the 60's early 70's for the E 13001 " 4 ATM ". 36 mm for the E 2638, 40 mm for the E 13001. Valjoux 72 for both of them. As well as screw-in case back. And a big ...