Need ribbed window track not sure what type of window they are
That stamp is very peculiar, but stamps aren't product codes or anything. They just indicate the strength of the spring. In order to identify the Series, we need to go by its physical attributes.
I will need to see a picture of the other end of the metal channel as well as a picture of whatever clip, hook, or shoe is at the end of the cord. I would also like the exact weight of the sash.
That's the top end taken care of, but we still need the rest of the information I requested. I also wouldn't recommend estimating the sash weight. In my many years doing this I've never seen anyone guess right. It's best just to get the exact weight to be 100% sure.