WOW.. have him safely pull the bullets and then soak the cases in water to disable the primers
or snap them in a .30 cal rifle( Looks like 3006 ammo) Hard to judge it from a picture, no scale to use.... Remember to remove all the powder and bullets..
The date will be stamped on the Bottom, along with the cal.. ie.. 1943 ammo will have a 43, 1945 ammo will have a 45 etc..
and a code to which factory built it..
I have ammo from the 30's that shoots just fine, I have to clean my Mausers very well after using it, corrrosive primers in this older ammo..
As long as ammo is stored in a Cool dry place it can last for Many Many years..
Oh, DON"T TRY and EVER handle Old stuff like this you have found, it can become very unstable after exposure to the weather and heat Etc..
I have many years of the shooting sports behind me, and been loading ammo, Making bullets etc, since I was about ten..
I am not concerned that someone with knowage, and experience handles Old exposed ammo like this, But to the inexperencied it can be dangerous..