Take off the rear side cover, it will unscrew. You'll find that you can change the power from a low of 2.5, 2.75 or 3 up to the high power of 5.
It's a DUAL power scope, not a real variable but I think it was Weaver's first entry into the field of scopes with more than one fixed power.
I'm sure you'll find some notation on it somewhere that says KV .
And some of the very early ones may not have even had the writing on it, so even if you can't find the writing, take off that rear side cover(smaller one) and turn it either direction while looking through the scope. The adjustment (under the cover cap) usually has an arrow on it with the power # indicated. Look through it, then try turning it. I think you'll be surprised and happy with the utility that you never knew it had!
Enjoy!