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Pentax FA* 300mm f/2.8 ED IF Lens 300 f2.8 SMC FA Star | eBay
It appears that this lens is missing it's filter pack. Frankly I got a set with each my 3 big FA* lenses, and I've never used any of them. It does look to be in especially pristine condition.
I've spent a small fortune with this seller. He cares a great deal about the lenses, and stands behind what he sells.
IMO, He's about $600 too expensive on this lens, but if you really want one, where are you going to get one? Especially in this nice of shape.
If you're thinking about buying, I suggest you ask him to perform a focus test if he can. As I've come to understand, many of these lenses require a substantial AF adjustment.