An AW Co model 57 question

[Tom Huber]

When changing a mainspring on the earlier model 57's, I have noted that the pillars beside the mainspring barrel are set too closely to permit the mainspring barrel to slip out. Thus, the plates must be disassembled to change a mainspring, and the barrel must be laid between the plates when reassembling. On later model 57's, the mainspring barrel will slip out and back in to change a mainspring.

I measured the distance of the pillars from the early to the later. The distance between the pillars center to center on the early 57's is just over 23 mm. The distance for the later ones is just over 24 mm. This 1mm change is enough to allow the mainspring barrel to be removed.

Obviously, AW Co re-engineered the model 57 at some time to allow the mainspring barrel to be removed. My guess is that it occurred around 350,000 SN. This was probably done due to complaints of watchmakers on the extra time needed to change a mainspring.

Now for the questions.
Has anyone ever seen a technical bulletin from AW Co announcing that they did this?

Does anyone else have any definitive info as to actually when this change occurred?

A curious mind wants to know.

Tom

 

[Dave Berghold]

Tom,
I've been a fan of '57's for a while and have noticed this too...though not to the extent that you have.... good investigating. I often wondered why the pillars were too close on some of the early models but never made heads or tails of it.

Dave

 

[richiec]

Tom, according to Ron Price's "Origins of the Waltham Model 57", the plate design was apparently changed around 1860 from a surround type of plate to a more open plate to allow main spring barrel removal without top plate removal. Hope this helps. This seems to be a lot earlier than movement 350000. Hopefully someone else more knowledgeable than myself will chime in and either confirm or refute what I just stated.

 

[Tom Huber]

Hi Richie, I'm aware of the change in 1860 when the wrap around was eliminated. This is post 1860 with the open side. From 1860 to around 1866, the pillars are too narrow to permit the barrel from being removed. After that the pillars were apparently widened.

Tom