Excellent find Clint
I agree with the Lohner M-type E18 and E20 identification.
However, with regard to UFAG W 13 I prefer Hansa-Brandenburg W 13 (UFAG) myself....
The double is actually of K307
I also wonder from where the seller gets Albatros sS4? I have never seen a photo of one, and no markings visible on the actual photo either. The flip side has nothing to say. Any good pointer?
Cheers
Stig