only5402
507
first make sure, that...
you collect all informations about the watch you are looking for - specially if it is a vintage watch.
Please do this for your wanted watch - the 5402 ST- generelly.
"a back replacement" is not possible, because it´s a monocoque case. The Ref you can´t find on
any place on / in the case.
If there is no mention / engraving that shows the combination, for example No A 1111 or No B 1555 or.....
you can´t know that it is a A series.
If there is any engraving left on the caseback (for example the Royal oak) look at it´s deepness (or no-deepness).
If there is no engraving left like for examle No A 1111 it is possible to find out the primary engraving it has once
by the engraved number on the caseback inside or on a document from AP about this watch.
This number inside has a logical system. I try to find out about this, but i´m only sure for A series:
Example:
caseback outside No A 666 is inside 67666
caseback outside No A 1666 it´s inside 80666
If you understand this, you can "built the "outside-number" backwards from the "inside-number"
AP changed the leading two numbers, if the "outside-number became more than 1000. The reason was that they
don´t wanted to change the "inside-number" from 5 to 6 numbers.
For B, C and D from 5402 ST there are other leading numbers or letters.
(I talked about the steel version from 5402)
regards
Stephan from Germany