Underwood-B (Singer) 2683573 was on GB not long ago. It was a mix-master with an Underwood barrel, but date of barrel was not listed or legible in photos.
UPDATE 2/7/21: I had written down in my notes that the barrel on this B carbine was “unknown”, but at the time I wrote this post, thought I recalled that it was an Underwood based on a photo from the side of the barrel. Dan actually had a copy of the GB posting that went through to the end of the auction which did have a photo of the top of the barrel. The barrel was, in fact, a Winchester with stamped “W” and Winchester stamped barrel cartouche.
Edited by SSNPingjockey - Feb 07 2021 at 1:40pm