First I will give you the details then a question. On a parts website I was trying to order the upper balance holed jewel for a Hamilton Grade 974(original cracked). The site lists two entries. They are as follows:
Hamilton 16s,old part number 465,upper balance hole jewels,2pc,hole 11,fits all excepy 950B,and 992B,genuine,p&i,nos.
next:
Hamilton 16s,old part number 465,upper balance hole jewel,3pcs,hole 11 1/2,fits all excepy 950B, and 992B, genuine p&i,nos.
My question is, What do the Hole numbers stand for,and what scale are they measured on; there being a 1/2 diffrence between them. Thanks for any replies.

Frank Juchniewicz

I could be wrong but I believe the number sizes reflect the pivot sizes of the balance staff measured in millimeters. Size 11 would be 0.11mm's. While 11 1/2 would be 0.115mm's. The "2pcs" and "3pcs" are abbreviations for how many he has available. I know little about Hamiltons but I would assume they use 5 jewels total for their balance assembly: 2 hole jewels and 2 cap jewels and 1 roller jewel.

John D. Duvall
NAWCC Member 144772
NAWCC IHC Happy Camper 192
Chapter 185 Watch Repair Moderator

Thank's for the reply John. What you said of the hole numbers are the pivot sizes for the hole jewels. I measured the one good pivot on the balance staff with a pair of digital calipers,and it came up 11mm. Had I done that in the begining,I would have answered my own question,but glad I asked,and received the answer from someone who knows.

Frank Juchniewicz