These are not tapes
These are not tapes that have been recovered. They are 16mm film copies of the original tapes.
Although Doctor Who was recorded on tape from day 1 in 1963, 2" Quad was so expensive it had to be reused. An old BBC VT engineer told me that in the mid 60's half hour of tape cost about 2 grand in todays money. So tapes had to be reused for their use to make economic sense. Think he said the aim was to reuse a tape 4 or 5 times for it to pay.
Who would be routinely copied to 16mm film (or occasionally 35mm) after recording (or even sometimes during transmission). This was because film was cheap, easy to handle and could be sent all over the world for resale without having to worry about lots of different TV formats or the fact that some places didn't have access to Quad players. Back in the UK it was also handy for viewing copies for internal use as it didn't need expensive equipment to be played back (if you thought the tapes were expensive, they were nothing compared to the machines).
It's quite lucky Doctor Who was an international hit from very early on as episodes have turned up all over the world, all thanks to the 16mm prints being sent all over the place.
Hopefully more will turn up, but as the years go by the finds are getting less frequent. Only one episode of 60's Who was never copied to film so is totally lost so fingers crossed!
As an anorak note (as if this post isn't nerdy enough) the first original 2" PAL videotape that survives for Who is episode 1 of the Ambassadors of Death broadcast in March 1970.