Ammo is right. I don't know the answer to the question either. The US went to anothe jacket some time ago. they have a system that also calls for liners but has a goretex outer jacket. I have three of them. Very nice system. they are good down to freezing but not much more. the commercial stuff from LL Bean and such will do a better job in extreme climates.
I just dug mine out of the closet after more than 30 yrs of storage.
It still fits.:
I doubt that I can get much layering in it though.:
It was a good design, good pocket locations, built in collar head cover, midwaist drawtite. And kept you dry as long as you treated it with the likes of CampDry repellant.
I'd rate it about +15degsF with proper liners.