Here is a picture of a hang-tag from
The Parker Story. The tag carries the odd line --
Length of Shell 2 5/8 Inches
and right below that
Use Shells 2 3/4 Long.
108998 01.jpeg
I recall seeing a hang-tag that has a
Chamber Length ____ Inches and a
Use Shells ____ Long, but I couldn't find it right now.
In the book
The Parker Story the Remington vintage specification sheets on pages 164 to 169 call for a chamber 1/8-inch shorter than the shell for which it is intended.