You can see in my sig, a sling with the parkerized frogs. Era wise, there doesnt seem to be a given date when brass wasnt used and suddenly parkerized was, and there was def a time when both were in service. So, its the M1907, as it was carried, as far as I know, into VietNam.
I'm trying to get a hold of some old service slings. There are a ton of them in an armory I'm trying to get. Theyre rotting and unable to be used, but the problem is how they have to be discarded. Certain items have to be destroyed. Many parts of service firearms have to be destroyed, and in some cases I know of, the web slings have been included. Theyre difficult to come by as far as I have seen.
Heres another oddity, I can find the mil-spec loops in 1" and 1 1/2", but not in 1 1/4". Even if I could find someone who can parkerize metal, I'd get the material and ship it...