Thanks for checking Cindrs; I'll get the exact mesurements at the weekend.
I have a few WW1 French75mm shell cases; which are very common here obviously. But there are some very rare models if you know what to look for!
I found an 1898 production case a couple of weeks ago; which is 2nd year of production. So a nice one to have.
Here is a link to a very informative guide to the French 75mm shell case identification, which you may find interesting. If you join the site you get to see all the photos.
75mm - Douilles de 75mm du canon de Campagne Modèle 1897 (75 DEC)