Capo is the brand of a bicycle shop and bicycle manufacturer based in Vienna. The company was founded by Otto Cap in 1930. Otto Cap was a famous racing cyclist, most notable for being one of a trio of Austrians who came 5th, 6th and 7th in the World Championship Road Race in Budapest in 1928. Otto came 7th, his brother Walter came 5th and Max Bulla filled the intervening place.
Capo are notable for producing hand built road racing bikes, with frames from the 1950s and 1960s sporting ornate lug designs and plenty of gratuitous chroming.
As far as I am aware, Capo derailleurs date from the 1950s and used a pull chain design reminiscent of a Simplex Tour de France.
Capo still exists, and has a history page on its pleasingly retro web site. You go to any of the information pages, and select ‘Über uns’ in the drop down menu for ‘Home’.