Lately, I have been seeing more watches that have strange jewel counts (13, 16, etc). I recently purchased this one off of ebay. It is a R.E. Robbins grade model 83 with 13 jewels. As you can see in the picture, there is a pinion that is not jeweled.

I have an Aurora that has the same configuration (I believe that was because they needed to add another pinion for the seconds bit ?).

Can any of you Waltham guys shed some light on why they just didnt add another jewel set to make it a 15j. Was there a market for a 13 jewel watch?

Just curious.

and the movement (which I should have uploaded first, duhhh)

There is no easy way to know what the planners were thinking when they came up with each configuration.

7 jewels are pretty important on a lever watch. Beyond that everything is open to discussion. A lot of Walthams were made with 11 jewels with jeweling on the escape wheel and pallet arbor i.e. 2 pairs. A lot of others were made with 11 jewels with all pivots on the top plate jeweled. It seems pretty clear that the second configuration was intended to impress the viewer. However, an argument can be made that the top plate needs jewels to protect the oil and that the pillar plate does not need because the dial covers the pivots.

13 jewels usually includes the pallet, escape wheel and 4th wheel. However there are lots of configurations. Waltham called these 13 jewel watches 3 pairs jeweled. I don't think any of them are 6 holes jeweled since that would require a jewel on the barrel. I also do not think that Waltham did any 4 holes plus 2 with all the top plate holes plus 2 holes on the pillar plate. The did use 4 1/2 pairs and there is a notation in the handwritten records for 5 1/2 pairs.

The technical reason for jewels relates to running friction, which is greater on faster moving wheels. Since the 3rd wheel moves much slower than the 4th wheel, it does not need the jewel as much.

Each jewel had to be made and inserted and the pivots running in jewels were smaller and more delicate. All these things added to the cost. If the customer did not care, the added pair of jewels to get to 15 was just added cost. Of course the same is true of all jewels above 7.

As Tom said the minimum for a lever watch to run well is seven jewels. After that it is very easy to prove that at least 12 jewels should be used for a watch that is made to keep good time. The pallet and escape should be jeweled because the extremely small forces that are exerted on them can easily be reduced by minor wear of the steel pivots or bushings. The hole on the 4th wheel on the dial side should be jeweled because it is exposed to alot of gunk entering it through the subsecond hole on the dial. I suppose it was generally jeweled on the train side for symmetry or aesthetic purposes. It has also been shown that capping the pallet jewels increases watch timing accuracy.

Frank"407" Kusumoto