Photo from Etsy Seller Laysdaysgoneby
78% all Virgin Wool and 22% Rayon, sold in 120 yard, 1 ounce skeins. Skeins were purchased individually, or by the box.
Advertising was completed in a limited market - Pennsylvania - and not spreading into other markets for several years.
I this 1965 advertisement, we see a rather significant change to the Duet blend -- now 38% Wool and 62% Nylon, as well as a price drop.
Spinnerin frequently promoted the yarns in mail order give-away's through the Judy Love newspaper column. In this case, an attractive two-piece suit with crocheted shell.
Spinnerin did not publish any pattern books solely dedicated to their Spinnerin Duet yarn, however, the yarn was included in several of the pattern book releases between 1955 and 1967.
Sales lightend up as, moving into the 70's, the average woman no longer knit their wardrobes, thus reducing the demand for dress yarns. The yarn made it's last appearances in 1971.
There are a couple patterns in the shop. I'm sure there will be more when I start working my way through the Spinnerin pattern books in my collection. As far as a substitute ... I can't say other than the typical ... a lightweight plied yarn that meets the gauge of your particular pattern.
Thanks for dropping by,