Interesting Juvela. Do your Uragos have very short headset stacks?? And what is the make of your headsets?
The more pics of Uragos I look at the more I think my frame is one. And the serial number style matches: 4 digits and underneath a U and two more digits. The fact that yours has the same "Bertin style" seat stay caps and presumably from 1960....
Does your confirmed Urago 1957 have the same type of serial number??