Before putting rare tapes in old - even yet unused - drives: TEST THEM for some time.
I've had the driver roll of a 6250 drive literally desintegrate and spread a lot of goo on the tape. As it seems, there's a friction clutch inside the driver roll and either the resin inside or the rubber can go bad, spreading the gooey and very sticky stuff all over immediately after being put to use. The tape was well beyond cleaning, fortunately there wasn't anything of interest on it.