My 16.5 says 16.5 and is Serial 27xxx. it is less than a year old.
You can upgrade the foam to cork. They sell sticky cork sheet at McMaster Carr (the thinnest cork gasket material). I bought some and it works perfect for use as a 2nd cork mat, and cost $3.
I wouldn't worry about the cover. You want the proper/latest pickup tube though, sounds like it was upgraded? Does the pickup look like pics of new ones? How well does it work?
BTW, to me it sounds like this unit was a little bit misrepresented. Low hours but 15 years old is a little misleading in my opinion.