A 1962 Seamaster came in for a full service, running but losing around four minutes a day and with a crown that felt loose in the stem. The owner wanted it kept original where possible.
Opening the case
The case back is a screw type, and it came off without a mark on the knurling, a good sign nobody had forced it before. Inside, the calibre 552 was dry at the balance and the mainspring barrel, and a light film of old oil had gone gummy across the keyless works. The dial and hands were untouched, with only a faint patch of lume loss at the tip of the seconds hand.
The mainspring had set, which explained some of the timekeeping trouble on its own. The balance staff and hairspring were sound, so no need to source a replacement escapement.
Parts replaced
New mainspring, a fresh set of gaskets front and back, and a period-correct crown, since the original had been swapped for a generic one at some point and no longer sealed properly against the tube. Everything else on the movement is original to the watch. The crystal was polished rather than replaced, as the pitting came out with a light buff.
Timing results
After cleaning, oiling and regulation, it settled at plus 3 seconds a day dial up, plus 6 crown down, well within what I expect from a 552 in good health. Amplitude measured 268 degrees dial up, dropping to 240 crown down, both acceptable for a movement of this age. It has been on the timer for five days now and has not drifted outside that range.