The #4 1/2 is the only Newhouse trap with the dog snap from the factory. The snap was not designed to hold the full force of the anchored trap, but to attach a log for extra weight. Here is an illustration from the Wolf trapping Book "How to Catch Wolves with the Newhouse Wolf Trap", put out by Oneida Community.
Here is another illistration fron the tenth edition Newhouse Trappers Guide.