Ha was just going to this this question my LGS has a used Marlin camp 9 with a plastic black stock it's got the folding folding shoulder shoulder piece is 469 a good grab only one magazine?
It sounds like a good buy especially if it is clean, to me, but I haven't really seen any with plastic stocks priced or sold.
What I can tell you is that the wooden stocked ones on Gunbroker tend to sit and do nothing if the starting price is over $600. The ones that start at a penny tend to go up to around $600.
My LGS has 2 right now, both pristine(but no checkering) for $850 and the other for $950 with original box, but they are just sitting there no takers.
Magazine are pretty much a non issue, the Camp 9 takes Smith & Wesson 59 magazines, I found them on Fleabay pretty reasonable.
Hope this helps.
Garry