I just bought a few dozen of these. Anybody know the history on them or have any pros or cons on using them.

I had a dozen years ago. I sold them not because they were bad traps. All my other stoploss traps were Victor round pan traps so I wanted more uniformity.
I have one yet today that I had in a group of used stoploss I bought.
Very strong trap with a nice pan and dog setup. The guard goes forward rather than back and is wider.
The chain attaches at the front of the trap and not on the spring, that can make working the trap a bit more difficult to set or move into position. Also with the guard spring forward if you spring the trap wile setting you get a nice bang on your thumb or fingers.
It may be a good idea to put the chain on the long spring. I have held coons with all of my stoploss and otter as well the Northwoods will hold up well also.

Bryce