I have two pieces of gear that contain v-belts, one designated K-31 the other K-27. They are 1/2" deep and 5/16 wide (although with minor variations - about 0.01" - they are different ages).
I cannot find any reference in any of the manufacturers' or dealers' web pages to a K-series.
Google is no help - the only relevant reference was a question on another forum with a bunch of singularly unhelpful answers (such as "Google it!")
Anybody has a clue? The nearest match I found was an "M" section belt but they seem rare as hen's teeth.