Thanks Rick, Zedder was the name I couldn't remember.  I didn't think they were still around!  www.zedder.com/itm00609.htm
 

That Zedder site looks very interesting!

I purchased that Zedder software years ago and used it all the time when i bought out Yamaha dealerships old inventory and sold NOS Yamaha parts on e-bay back when all this NOS parts on e-bay stuff just started out and used the parts on my restorations. It was very useful for my listings. Did that for at least 2 years non stop maybe longer. 
I didn't know it was still available. I think i received it on a disc?  

The other thing is oil and the friction material and the matrix its attached to. 
As time goes by in certain atmosphric conditions acids are formed in the oil. Combustion does this in 4 strokes. Maybe. The matrix on alot of the old plate sets I've taken out is a resin type material. The friction pads are an asbestos compound maybe a chemical reaction with some of the oils causes the plates to swell and once they've been saturated the Simpson persists.
Of course I could be talking total shite