I guessed on the 40lb's but they don't make them like that anymore... at least in a retail setting. How much did it cost you to have yours refurbished?
Couple of tips or/what to or not to do on your cleaning solution... don't use regular water, use distilled water. Be very sparing with the rubbing alcohol, if you use too much it will eventually dry out the grooves. If you can get a hold of a small bottle of film processing fluid that would be great... it helps keep a nice sheen when you are applying the liquid... just a few drops.
Here is what I use for the Nitty Gritty:
8 oz bottle
1 drop of Dawn
4-5 drops of film processing fluid
Tiny bit of rubbing alcohol, like 1/2 a capful if that
Fill with distilled water and shake.