How old is my Wild instrument ?

A frequently asked question is, "How old is my Wild Heerbrugg instrument?".In some cases this is a very simple questions to answer, in others much detective work is needed.There are a lot of different serial number lists. The following data belong to Levels and Theodolitesand are estimated, not in every case actual.
For other instruments and more accurate data please send me an email with the serial number, the instrument type and a photo.

Here's an example out of the Geodesy folder. It is the first page of the "subtense  bar". According to the list it was first produced as T7 1929. Starting in 1956, then as BL (BasisLatte) 1966 as BL21 and from 1967 to 1985 as GBL3 (Geo-BasisLatte version 3).
Specifically, here is the fact that from 1969 was again further numbered with lower serial number.. This creates the strange situation that a higher series number is not neccesarely the newer subtense bar.