Now, this is a bit of an obscure yarn; evidenced by it not being referenced over at Ravelry! A Google search rendered nothing, but did find a few tidbits in the old newspapers.
This advertisement, mid 1950, tells us the yarn was a 3-ply Fingering yarn. The two patterns I've found indicate the yarn was also sold under the Bucilla name, but I've found no such tracks.
Picture from Ebay seller CaliforniaGold
So, what did we learn? Lanadown Yarn was marketed under the Bear Brand (Bucilla) labels between 1948 and 1953. It was a 3-ply Fingering Yarn, 100% Virgin Wool, in 2-oz skeins.
I have only two patterns, at this time, in the shop that call for Lanadown yarn. They both come from magazines. I don't know if any of the Bear Brand pattern booklets promoted the yarn, but have many in reserves waiting on me .... who knows!
So, should you come across a pattern calling for this yarn, hope this will help you finding a substitute .... any 3-ply fingering weight yarn should do you.
Thanks for dropping by,