I just stumbled onto a Mauser 660 5 barrel rifle set. The set is in a fitted case and comes in calibers 30-06, 270,7mm etc. ANy idea of value of this set? I have seen sets of three but never 5

Very limited resale value in the sense that you have to find someone who just loves the Mauser 660, and, doesn't mind the overlap in functionality of the barrel choices! Newer rifles eg. Blaser, give (IMHO) better design and barrel interchangeability.
Just my $0.02, Peter.
PS. If you do an internet search you will see that Cabela's has a 3 barrel set for $2800.

I purchased a Model 660 in .308 in about 1974. It shot rather rather poorly. Worse, it kicked like a .458. Well, I got married, needed some money and sold it. Well about 25 years later I bought another one. I took it to the range and quickly discovered why I sold the first one. It too kicked like a place kicker for the Packers. I'm a sucker for German rifles, particularly Mausers, but these are more interesting to handle and discuss than shoot. I'm used to shooting a .375 H&H so the fact these 660's kicks so bad is not my imagination.