Having gone through prints and negatives from my great-grandparents, It's thin, thinner than computer paper even, I think. Though it's also fairly tough feeling. It has a sheen to it on the borders that's a little like Art300, but there isn't really much texture to it. Does such a paper still exist?
Just scored some paper that is just a little out of date. Barnet Bar-Gas, Agfa Brovira, Gevaert Orthobrom, along with a selection of Ilford and Kodak Bromide papers - One is a white fine lustre single weight which might be a close match for the stuff you are looking for.
I'm going to try some this evening just to see if it is any good after nearly sixty years of unknown storage conditions.