A yarn that fits the bill perfectly is Cascade Heritage Sock Yarn. I have used it for several of my "vintage" sock projects, including the Gentleman's Golf Stockings pattern that was published in Interweave's Unofficial Downton Abbey Knits magazine:
Heritage Sock is a great value! 437 yds per skein at $11.00, that's a steal. It's 75% merino and 25% nylon, perfect for comfy socks that wear well. It comes in a nice range of solids, plus tweeds and handpaints (those cost a bit more, but are lovely)
I was so pleased with the way my Gent's Golf Socks knit up with Heritage; the color work on the cuffs stands out beautifully. I'm going to knit another pair of 1890s stockings (soon-- just need to finish about 85 projects lol), and this yarn will definitely be the one I use.