To soften dry stiff leather Mink Oil or Neetsfoot Oil work great. Saddle Soap is another one for overall conditioning. There are others, but I've never had a need to try any more.
If I had to guess I'd say the stuff you've got is something like Mink Oil. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />
Oh, and Atom Wax or I think it's Weather Seal (It's kind of a Wax treatment too if I remember right) can be used as a sealer.
Well, it's definitely an oil, murky brown in colour, and typically I soak a little into a rag and rub it gently into the leather. Great stuff, it doesn't discolour any of the leather, and waterproofs it as well; water just beads on it. Does this sound like mink oil?
Neetsfoot oil..? Never heard of it; remember hearing about Saddlesoap from my cousins on the farm (Naturally, they use it on their leather straps and saddles! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />)