I'm using Lily 18th Century 100% Mercerized Crochet & Bedspread Cotton that I found in my stash. I think it's size 10, but it feels softer than the size 10 balls of Knit-Cro-Sheen I have stashed.
Not sure when or how I acquired it as the thread has been discontinued. The labels say the skeins were bought at Woolworth's for $2.79 each; it's been many years since I have shopped there.
I still have to reach my desired length, add sleeves, make the buttonhole band, and add buttons. I have 3 skeins and each skein has 450 yards. I'm on my second skein so should have plenty of thread to finish the project.