Wildcatter,
I have emailed you the contact address and individual's name with J.P.Sauer & Sohn in Eckernford, Germany.If you don't get my email, let me know and I'll try again.
Sad to say, but the Sauer records are far from being complete, I think. From the contact point that I have given you, I learned that all records were burned before the Russians took over after the War. This included all records of production, description etc all the way back to Day One with Sauer. I was told that when the Company relocated to Eckernford an attempt was made to reconstruct from memory what was known at that time.
Good luck on your quest....sure would like to see photos of your Double!
