Jon Zimmer sold one for $65. His description was: "DURY & SHINN MFG. CO, NY, UNIVERSAL SQUARE, Pat'd May 18, 1902. 11 inches long. Has 90 and 45 degree edges and an offset 90 degree angle that can be setto different rafter pitches to mark the ridge-cut, bird'smouth and rafter tail, G+ .......... $65.00
Another was in the May, 2010 Antique Auction, no description.
Worthpoint lists two, (attached picture captured from there). One describes the tool as: "Rare Universal Carpenters Square by Duby & Shinn patent date May 13, 1902. This was the early 20th Century answer to the combination square and the modern day speed square. All steel construction. It was a handy framers tool for roof layout, scribing lines and other carpentry tasks."
Another went at 3rd Annual St. Charles Antique Tool Auction, Oct 02, 2010 St. Charles, MO
For a measly $10
All these are specified as being made of steel, so if your's is brass, I think you have a seriously rare item.
I know I've seen one before, and I thought it was made more recently, but I sure can't find anything else. I think Jon's price is closer to the mark. He's not anything like cheap or bargain, but I think he knows what he has, and is fair.