I am going to start a collection of the Blake & Lamb double Underspring traps. I am trying to determine the years produced, values, the difference in sizes between models such as #44, #40 and #4. Why some have teeth, and some had more rounded jaws. These traps seem to me to have been a better choice in beaver trapping back in the day, when it came to size and weight while packing all your worldly possessions on a string of horses and mules, probably a better choice then double long spring traps. Anybody help me out with some information on these, before I start investing more of my time and money ?

I still use the double jumps. I think the #2 and 3 is the perfect mink trap. Low profile, bigger stock pan, somewhat lightweight. I found 2 problems with them- I have to set them with my feet and after awhile the spring edge gets a groove worn from the side of the jaws allowing slop. Ive seen some you could pull the jaws apart almost 1/2" from wear.
I cant help you out much with their history, I know they been around for a while.

I had a couple dozen of the 40s that I bought from a widow of a deceased beaver trapper back in the mid ‘80s and didn’t have much success with them. Maybe it was me but I feel they lack holding power by design. The 44 dus was a little better and the 44 longspring version was far superior and it looks like bridger modeled the #5 after it. The 40 and 44 double undersprings were improved slightly in the tooth models.

Still use the 44 us's,agree the 44 longspring was better.Loved the 44 us with teeth,definitly improved its performance on Beaver.

Thanks guys, You have been helpful to me and I'm picking up some information on these traps.