Old Egg Scale

[Unclebean]

Does anyone know what the numbers on this egg scale represent? The numbers go from 19 to 30. My MIL had this and gave it to us. I don't know how to convert the numbers to egg size. Any help would be greatly appreciated!

 

[Mac in Wisco]

It took me a while to figure out, but I think the numbers represent the standard sizes in ounces per dozen.

Jumbo (30 oz.)
Extra Large (27 oz.)
Large (24 oz.)
Medium (21 oz.)
Small (18 oz.)
Pee Wee (15 oz.)

 

[Klukkin Ken]

Heres one that converts those numbers to grades.
http://www.enasco.com/product/C28431N