I've been working on a lot of Pierce chronographs lately and I just encountered one that has a number of features that I had never seen before.
First of all, the movement is marked 134 with the Pierce Pi logo.
Then it has a real ratchet wheel click instead of the usual wire click. This version can actually be accessed from the train side of the movement so the dial does not need to be removed to let down the mainspring.
The clutch disc is a rubber washer enclosed in a metal ring. Is this original or a later replacement?
Finally, it is not marked with the letter M which I have seen on all other caliber 134 movements (By the way, what does the letter M stand for?). I assume that this is just a very late version of the Pierce 134 chronograph but I have worked on many and this is the first one that I have seen. Any thoughts?
Jeff Grieff

First of all, the movement is marked 134 with the Pierce Pi logo.

Then it has a real ratchet wheel click instead of the usual wire click. This version can actually be accessed from the train side of the movement so the dial does not need to be removed to let down the mainspring.

The clutch disc is a rubber washer enclosed in a metal ring. Is this original or a later replacement?

Finally, it is not marked with the letter M which I have seen on all other caliber 134 movements (By the way, what does the letter M stand for?). I assume that this is just a very late version of the Pierce 134 chronograph but I have worked on many and this is the first one that I have seen. Any thoughts?
Jeff Grieff