The "Variable Ledge Priof Finish" is illustrated in the Illinois Glass
Company catalog "B" that was probably issued around 1927.  Page 114 of that
catalog shows this finish for wide mouth jars and page 154 shows it for
crown like bottles.  Both show that the bottle could be opened by sliding a
coin between the ledge and the top for prying off the lid.  Neither page
lists the date of the patent.  Page 114 states:

" The sloping, variable Priof ledge permits any flat metal instrument to be
used as a lever in prying off the cap.  With this finish the crown opener,
while still effective, is no longer essential."

Peace,
George L. Miller
URS Corporation
561 Cedar Lane
Florence, New Jersey 08518