What are these from?

There are a lot of step down power converter modules (identified as KIS-3R33) around on the internet using the MP2307 buck converter chip, usually advertised as used, taken from a machine. I was thinking of getting a couple to make a lab psu out of instead of a linear regulator.

Does anybody know what they are actually taken from? There must be 1000's available from various sources.

That kind of down converter has so many possible uses the chances of you tracking down what it came from is virtually zero.
If you're going to use it for a lab supply you'll want a ripple rejection filter on it as well.