you must make sure what you actually need and dont get confused with their weird version numbers.
i dont know it myself, but i
think that at the times where the last soft sample cell came out the ilok usb dongle didnt even exist, and it was using the interlock serial/response system. but i could be wrong.
the basic rule is: when you install a legit product, older products will always still work with the latest driver sofware from pace.
other "versions" of products might cause unpredictable issues.
in your case, 505 should be okay.
in my opinion it is a bit strange that pace as a third party supplier stopped support for OS9 long ago.