1. As mentioned on the serial number thread there was a change from the bolt on corrector retaining ring to a screw on one when Criterion brough production of the corrector cell in-house - this happened sometime between serial number 4268 (mine) and 4627 (Neil/apfever's).
2. The casting for the fork tine carrying the declination circle also was changed at some time between serial number 4268 and 4627 - my declination circle stands out from the arm as shown below whereas that on Neil's is flush with the arm as can be seen in his picture on this thread - 5th pic down on page 1.
3. The declination slow motion was changed from some other arrangement (shorter arm?) to the tangent arm that reaches to the bottom of the fork tine at (I'm guessing) a fairly early stage in production as most of the pictures I've seen show the long arm. A couple of pictures that show the earlier arrangment are here and here. Both these units are in the earlier dull blue colour scheme.
A few questions:
- What was the reason for the change in the declination circle fork tine casting?
- What was the earlier declimation slow-mo arrangment?
- When did these cahnges occur?
- Are there any other changes pre B&L?
Thanks for any further information.