With 4 winds the amplitude is 250 and rate is still 999. The regulator is set as far to slow (near end curve) as possible.
This mainspring is from the donor. It looked cleaner than the original. I don't have rewinding tools so don't clean the mainspring.
I'll transfer the original mainspring back this week. However, the donor watch looked ok on the timegrapher. Is it possible that the donor hairspring will only work in the donor watch? At the moment the watch has a donor balance cock and jewels, donor hairspring and mainspring.
I have loads of books but have not seen any references to this type of case.
I would say that most books have photos of the dial side but do not show photos of a virtually plain solid back.
I was asking if anyone knew of this type of case and how I could get into it
The one which uses this back, I have found, is mostly the Dynamic model which I have never been drawn to, so had no need to investigate. Hence my lack of knowledge.
You seem to have taken some offence with the post, I don't know why, but a bit of help with a simple problem would have been appreciated.
As I said earlier I got help and explanation from another source and now know more about this watch. Surely this is what collecting is all about
Same, for a reasonable price: https://www.aliexpress.com/item/2029153808.html
BTW, my Chinese 5700 doesn't any of the issues described by the OP, and works perfectly. However, the casting isn't perfect, and the some of the bits sent were duplicated. I remedied that easily on the lathe,