Vintage SEIKO 7005-8022, ca. 1974
Due to the service marks I found inside the watch, I can tell the decade. That decade is always the unknown factor when deciphering SEIKO manufacturing serials. But since the watch had been serviced in 1979, the year 1974 makes most sense!
Interesting also that the punching of the serial numbers is so irregular. I had a discussion with Ty recently on the PMWF.com forum where we discussed about the serial number stamping on SEIKO backs. Ty suggested that the first two and last number are printed later. The frist two representing the Year and Month of assembly and the last digit the assembly location code. But right now this is an assumption. If the assumption is confirmed, I will update this page.