I had a Purple Rhino Pro back in the day and it was my very first reactive ball.  Back then, it worked well on medium patterns really well, got into a heavy roll and was very predictable.  My dad had a Teal Rhino Pro and that ball was meant for heavier patterns.  It hooked a few boards more from what I remember. 

Today, it would probably be a good light oil ball as it would give good control and a predictable shape overall. 

What color is the Rhino Pro that you picked up?

Go here:
http://www.123bowl.com/search.cfm?companyID=5
Enter "Rhino" in the field next to "Brunswick" and hit "Search".

It will show you just about every Rhino made.

I got a rhino pro bowling ball from a thrift store this past weekend. I clean it and it still works a little but I'm trying to get control of it. Anyone on here had experience with any rhino balls?

I had a Rhino Pro LE which was one of the best balls I've ever owned.  Had several 700's with it.  It would work on heavy and, with a slight surface change, would also work on medium conditions.  Mine got messed up a bunch of times in the ball returns and, after it was resurfaced several times, it is too small to work in the returns.  If I could find them new, I'd probably buy a case.

I had a Black Rhino and a Teal Rhino. Both were urethane as I remember. The Black Rhino was more useable on medium and light oil patterns. The teal was very pretty, but I used it as a spare ball and eventually gave it away. It barely hooked at all, unless you were on a torched pattern.

I also had (may still have) one of the Black Rhino's...seems to me it was late 80's but no later than early 90's, and that was in the days of short oil.  And yes, the Teal, if I remember correctly, was designed for what would have been considered dry IN THOSE DAYS.  Even wet in that era would be viewed by many as dry in today's snow-tread-in-a-box climate.