Yep, it's an ADGA. I have one just like it on my commuting bike - came off a Peugeot UO-8 that I bought in 1972. I find it very comfortable. Even though this was common on inexpensive bikes, and it is a couple of steps down from a Brooks or an Ideale, it is certainly worth using.
I think that it was not original on your bike, but still better than some of the replacement saddles out there.