A beautiful collectors piece now, as these are very rare ratchets. The mechanism design came from a gentleman named Gideon Gagne who patented it for Snap-On in 1935. Despite the popular opinion for these mechanisms being weak and crude, I find it to actually be very strong and stout. It is a dual pawl 42 tooth internal toothed head with a 2 tooth per pawl engagement. That's 4 total opposingly directional contact teeth in each direction. These day's that's really nothing to shout about, however remember, this was the early 1950's. The selector is interestingly unique, I think of it as a helicopter chopper. But the feature I find most interesting are the threaded retaining plates. They use a two 1/8" pin spanner type wrench to remove counterclockwise. These plates can be very difficult to loosen without damaging the pin holes. Luckily both of mine came off relatively easily with my own custom made spanner wrench. Overall I am happy I purchased this particular ratchet, as it's value will most likely increase as the years go by. It will never be used by me, as I said it's now a collectors piece, only to be admired and gazed upon. I usually don't collect Snap-On, however I have a interest in these particular round heads, as they have their own story behind them.👍