Could someone explain this to me:
What is meant by Pairs?

“Jewels” or “Jewelling” refer to the number of jewels used in the watch to reduce friction on the bearing points. 7 jewels are found in the escapement, and additional jewels – if used – would typically be found on the plates for jewelling the gear train. Notations found in the database are as follows:
• “Plain” 7 jewels
• “4 holes” 11 jewels all in top plate (looks like 15J)
• “2 pairs” 11 jewels
• “3 pairs” 13 jewels
• “4 pairs” 15 jewels
• “4 ½ pairs” 16 jewels sometimes have cap jewels in addition to hole jewels
• “5 pairs” 17 jewels usually have cap jewels in addition to hole jewels
• “5 ½ pairs” 18 jewels (?? I don’t think this appears.)

The pinions have an upper and lower bearing surface(hole) so in the case 11 jewels (4 holes) the upper visible are jewels and the lower are metal bearing surfaces. Add the 4 lower jewels and you have 4 pairs(15j). The other type of 11 jewel mentioned has an upper and lower jewel but only for 2 pinions.

I call a watch "honest" when Jewels are "paired" as Claude explains. The only value in jewelling a wheel is when BOTH pivots are Jewel supported for a "no wear - no service" performance. When the jewels are on one plate only for "show" the watch jewelling is useless, no better than a 7 Jewel movement for service sake as the unjewelled pivot will wear out faster and need re-sizing with every other service. "All show and no go"

Thanks Claude and David,
Now, I'm beginning to get it. I reckon you can't judge a book by it's cover. (Or, know the jewelling pattern just by looking at a movement from one side?)

HI Dave, Hope you don't nind if I butt in like this but it just happens I came accross this subject a while ago on an 1870 Elgin J.T. Ryerson. I was quite surprised by the absence of jewels on the dial plate, (where nobody can see them). It is an 11 jewels movement. I even took a picture, and here it is

Yea, this is a good example. That's why I couldn't understand the idea of "pairs".
Up until now, I would have assumed that the jewels in any watch would have an opposing jewel on the other side!

Peter that watch you show, s/n 121077 is recorded by Elgin as Grade 55, 7 Jewel movement, some being the signed Ryerson model. The top plate has evidently been "up-jewelled" to make it 11 Jewels, and it is a good example of a overjewelled "for Show" watch, and also an interesting variant of a 7 Jewel factory movement.

HI David, thank you for the info, yes, I thought this watch to be a bit odd, it is the oldest american pocket watch in my collection. I also find it strange it is listed as hunter, not as open face.
They did not mention the upjeweling on the plate, you would think they would have used it as a selling point, unless it was a special order..God only knows what was the reason, 142 years ago.
Here are some pictures of the watch,I found some of the patent details interesting, please let me know if you find something else about it.