This is a vintage yarn, most likely from the late 1940s to early 1950s, based on the label and the put-up in a ball. It is probably similar to the older 2-ply Saxony yarns that were sold for making baby items.

It is a somewhat lofty and elastic yarn, even for being so thin. On a yardage basis, it works out to be equivalent to 509 yards/50 grams.