This one is marked only (circle) 12.
The default was 65mm; variously given as 2 1/2", 2 9/16", or 2 5/8".
If it doesn't say 70 then it is 65.
The shorter shells for older European guns are available.
Gamebore gottum.
http://www.gamebore.com/page.php?id1=2&id2=4