Mainspring source

The 'D' does indeed mean date. Bestfit shows no listing for this movt, but it is a modified Buren cal 06. 

Mainspring dimensions are 1.00 x 7.00 x .08 mm according to Doc's site. If you have a mainspring book, you can find other calibres that take this spring. 

On second look, the above dimensions don't make any sense. 7.75 ligne automatics aren't all that common, but should take similar mainsprings. Bestfit lists mainspring dimensions in Dennison. 

Doc has left out the length in the above dimensions, but there should still be only three numbers: Width, Thickness, and Length. Maybe Mike can comment on this? Since there is no listing in Bestfit for the Buren Calibres, either, I can't find a Samson number. 

What you are looking for is a 7.75 ligne, slipping bridle automatic mainspring. 

Hello,

 The mainspring for the 7edad is the same for a omega 670. The bestfit # is WA28 and the marshall # is 5116. 

 Hope this helps.. Mike.....

It does, Mike, thanks. I'm going to make a note of it. Where did you find the dimensions, do you have a Bulova spec chart?

No, I dont, I was on the phone with my supplier, and I happened to be reading some post at the same time, so I simply asked my supplier.

 The info is not in the older bestfit or Marshall books.

 I think they said the spring was 5 x 15 x 8 1\2 ?

 Mike..........