This Seiko Diamatic 7006-5000 oval dial watch dates back to April 1972 — nearly 50 years. My friend Bela dug it out of the back of his closet, in its original and much-mildewed box. He said he’s gone through 3 watches since he last wore this, so knowing him, that’s about 25 years. He’s never given it a service as he can only remember “changing the battery”.
I had a hard time adjusting the watch, so I unraveled it and here’s what I found:
It has an unusual case-within-case sandwich design and obviously has been well-worn and suffered from corrosion. I threw in in the ultrasound cleaner for an hour, scraped and polished a few things, and it ended up like this.

Unusually the bracelet is 24mm wide and it took the longest spring bars I had on hand. None of my straps would fit due to the case curvature between the lugs. But it looks ok now if you ignore the scratched crystal. I found another for $20 so soon it will be smiling.
