There were at least two different styles in WWI. But both were leather. One is a pre war that was a fitted leather case with 8 loops and a web sling. The ones produced during the war were an easier to manufacture leather case that is not as fitted. The war made ones are about an inch shorter than the pre war cases, and it has 6 loops with a web sling.
I write on the 1903A1 USMC Unertls too, and there is at least one aluminum metal tube case that I have seen for a 24'' long Unertl scope, that has a connection to the USMC. But I haven't seen a metal one for the A5.
At least not in sniper production. I have a lot of Marine team docs for National Match teams and those guys used so much stuff.
The Marines used the A5 on and off again till the last mention I see is in 1944 when the disbanding Raiders gave 20 of them to the 5th Marine division.
Sometime if you ever think about it, send me a pic of it, I can see if it reminds me of anything. cplnorton2@yahoo.com is my email.
The case he had was bell shaped towards the top to allow for the rear adjustable mount to fit. It had a single sort of tool box type latch, and was aluminum from what I could tell?
If he brings it back to our next show over Thanksgiving weekend I'll get pictures of it. Sounds like maybe it's an Unertl case with an A5 in it.
I have several A5 scopes, but none have the ring turned down as you pictured above. So likely never been on a sniper '03. They all came on old single shot rifles I've purchased.