Glass sizes

[cadmaster]

Can someone explain the glass sizing systems?
I have seen glasses of similar size with labels saying eg "509" and "22 9/16" neither of which seem to relate to the actual size in inches or mm.
I have also seen two sizes on the same label eg "22 9/16" and "25 1/8".
Cheers

Martyn

[cadmaster]

Can someone explain the glass sizing systems?
I have seen glasses of similar size with labels saying eg "509" and "22 9/16" neither of which seem to relate to the actual size in inches or mm.
I have also seen two sizes on the same label eg "22 9/16" and "25 1/8".
Cheers

Martyn

[Jon Hanson]

Different numbering systems; several companies used an inventory number, e.g. "509".

There is also sometimes a single number 1-8, usually at the bottem, which has to do with the height of the crystal: 1-3, high dome; 7-8, for hunting cases.

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Jon Hanson, nawcc#8801

[jagkar]

OK here's half the answer--one of the numbers is in the curious quantity "ligne", =.088814 inches. Correctly pronounced like lean-ya (with the last syllable half swallowed), most Americans mangle it "line."

[Julian Smith]

First of all,all crystals were not marked in the same way.
Most have a 3 digit number on the top of the label.This is the measurement in hundreths of millimeters.508 would be 50 8/10 MM.The next number down is in lignes and sixteenths lignes.Thats why they go to 15/16 and then to the next number.I have no idea what the third number means.
Different manufacturers must have used a slightly different scale 'cause the same marked size by two companies are sometimes different sizes.
Good luck,
J Smith

[Dave Haynes]

All I know is that all the sizes I need, for 16s and 18s are gone and I have hundreds of sizes that do nothing! Those crystal assortments were a winner for their marketing department.

[BrianC]

Martyn,
I have some papers that explain the numbering systems with charts on glass crystals. If you would like a copy, send me a business size sase.
Brian C.

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[Jim Carroll]

I also require some help with this problem of crystal sizes, I have a collection of Illinois Extra Thin Watches. and would like to replace to the original crystals, on Keystone and Wandsworth cases. I have bought crystals on ebay and had no success.
Coming from Scotland does not help.

[cadmaster]

Many thanks - I think I have a grasp of the mm and ligne systems now, though the second size labels are still a mystery (a different ligne scale perhaps?).
On a related note - determining the correct crystal size? I can measure the inside diameter of the bezel - how much extra do I add for the groove to achieve a good 'press fit' (my interest is mainly in English watches, which never used glue)? Acrylics should be no problem - as long as the crystal is a bit bigger then the glass press should handle it, but for glass...?

[Kent]

Here are a couple of sheets that explain the Crown crystal sizes.

Explanation Sheet (http://www.midwestcs.com/elgin/scans/misc_ads/1927/m_crown_1.html)
Chart (http://www.midwestcs.com/elgin/scans/misc_ads/1927/m_crown_2.html)

Kent :smile:

[This message has been edited by Kent (edited 08-28-2002).]