Here are two of Southworth's Business Papers, in 25% and 100% Cotton.
The 100% Cotton paper has a tooth to it, not unlike G. Lalo Vergé. Some like that kind of thing, but I do not. You definitely feel it as you write. But as you can see, the line quality is quite good.
The 25% Cotton is a lovely paper. Smooth textured without feeling glassy, the line quality is good and some shading can is evident: I will have to experiment more with some shading inks. I will be picking some of this one up.
Both papers are watermarked, with security code. Both are 24lb weight: showthrough/bleedthrough was zero.
Full res images here:
Hope this is of some use.