A. Lange & Söhne

Very nice engraving on a pocket watch I picked up recently. I date the watch somewhere around 1880 but I am not sure what the significance of the 20 is? ...  

The “20” appears to refer to the number of jewels (“rubin” = rubies).

Your watch is not ordinary pocket watch. It was made in 1878 (according the case number) as Fu (=Futter), it means 1a quality (Fu was used instead 1a before 1893). It should be a pocket watch with date and central date hand. In 1877 Lange produced 3 date ... 

I really appreciate this info, Serge. The watch does have a date complication but is not central. Here are additional pictures. ...  

At that time Lange produced mainly central date hand watches, as below (1st made in 1876, 2nd with seconds subdial - in 1882) WBR Serge ...  

On a serious note, thanks for sharing brother. Truly appreciated. You alone is a reason to visit Minsk!

And as I see these timepieces, I'm desperately waiting for 1815 with central data hand ))) WBR Serge