On p. 164 of Houchins is a "early style engraving" for No. 4, that is similar to yours but with a setter on the left lockplate
I found this image in the 1903 Dunham, Carrigan and Hayden Co., San Francisco catalog which looks JUST like yours, but the image must be a No. 3??
Are the barrels marked Armor, Crown or Nitro Steel?
Please have a stock specialist evaluate your stock - it looks to be in need of glasbedding around the lockplates, esp. the right. The top lever screw also needs to be replaced.