The 16 in a circle indicates 65mm (2 9/16")chamber length. If it were 2 3/4" it would show 16/70. Most German guns of that vintage have 65mm chambers. It is good to check the chambers with a gauge to see if the chambers have been lengthened.

Cheers,

Roger


C. Roger Bleile
Author of American Engravers-The 21st Century
FEGA Historian
www.engravingglossary.com