As mentioned above that's a pretty good find. I have revived many vintage strops by this method.

Cleaning with a touch of saddle soap and barely moist cloth.

If it's dry, I will rub in dabs of Neat's foot oil on both sides of the leather. I masage the oil to the leather until it feels like healthy leather should.

I work the leather over a rounded edge of a counter top. It looks like I'm buffing the counter edge. I do this on both sides. I do this until leather feels supple. I also do this with the new strops I make.

Then I go after nicks with fine 220 sand paper. Gashes or deep nicks, I'll start out with 150 and then finish with 220. If the leather feels very slick I'll run the 220 lightly over the finishing side to help with the draw.

This will do wonders for an old veteran strop.