I found this film recently and although I think I've never used it in the distant past, I'm not sure.
How do I know for sure?

I'm pretty sure as best my memory is ,in my filming days the film when used used to say"EXPOSED"on the end .
I stand to be corrected that was some while ago.

Have a look at this. Not sure if it also applies to Agfa.
https://photo.stackexchange.com/question...THE%20CARTRIDGE.

Gwyn, thats correct, if the word exposed, cannot be seen when you take it out the camera, there's a chance it hasn't all been used.

In the past, we did shoot a lot of stuff on the 50ft cartridge's, Kodak mostly but also Aga, "Exposed" was what you wanted to see when it was finished. I also recall a few instances where the camera's indicators stated film finish, (or whatever) but when we took it out it wasn't. It back in the camera for a few more feet and when the sound of the cine camera changed, thats when you knew for sure.