Swapmeet find

At the local swap this morning I picked up a virgin TK70 streaming tape drive. When I say virgin, I mean it is in the shipping carton, is still sealed in an anti-static bag, includes the manual, and also that sheet of 'stickies' to make the meaning of various lights and such meaningful to those who do not understand English. In a discussion of COMPACTape II, it was stated that those tapes were interchangeable with the earlier tapes in the TK50 drives. It was also noted, as has been covered here several times, that if written to by a TK50, the tape was readable by a TK70 but could not be written to by a TK70. This is the first time I have heard that the use of the II tapes in a TK50 was a factory authorized usage. Interesting! Perhaps useful considering the scarcity of the older tapes. Question: Can a TK70 be used as a 'drop-in' replacement for a TK50 in a VAXstation 2000? If so, I would assume that it would NOT record at TK70 density. - don