I have an Elgin sent to me as a parts unit that I ended up fixing instead. It's a 16s, 17j, OF unit that was missing the balance system but otherwise in good shape. After a Ultrasonic cavitational cleaning in Zenith 67 @ 90 F and reassembly with newly found used parts it took right off. I made a daily carry watch out of it and it was right on the money every day. Needing to carry another unit for checking its performance I benched the Elgin but kept it wound. It imeadiently fell about 80 seconds slow every day. In my pocket with the parts warm and expanded it runs on time but cool it down and it slows down. Expansion and contraction go with heat and cold but have you ever noticed this on one of your units? The tolerances are so tight that a little heat loosens things up and it has the freedom to run?

Patrick-

Probably has to do more with what position the watch is in when it is running. Try setting in a stand and see how it does with the stem up. also, I look for equal balance motion in all positions of the watch after I have cleaned them and put them back together. If the motion slows at all in any position, then something is causing the watch to slow down in that position. Something to think about.

Jared