The filters in the marketplace aren't very good, because they are actually just tags the creator needed to specify. In principle you should be able to say, "I have Poser 11, show me any content that will work", but it will only show the ones the creator explicitly said "Poser 11" for. Something from Poser 9 will certainly work, but they might not have checked that box.

It would be pretty useful if there was an option to pick "any Poser" rather than having to specify a specific version, because picking any specific version will filter things out. And if you pick multiple versions, it only shows items tagged for all of them, so that gets you even less.