All or some episodes missing from the above stories shown in red. So it could be one or more episodes from the above stories.
Frazer Hines has also been reported as appearing at the event, he appears in all of the above stories, and the following stories that have all or some episodes missing.
All the above are Patrick Troughton stories. But now I hear Peter Purves is also being reported as being at the press conference, and he was only in William Hartnell stories.
So for my own amusement here's a list of the stories with missing episodes featuring the god like genius and Blue Peter veteran Peter Purves.
Mission to the Unknown
The Dalek Master Plan
So I'm figuring at least a couple of episodes, one from the Hartnell era and one from the Troughton era. One things for sure, no episodes were recovered form outer-space.
Now it seems Peter Purves isn't going to be at the press conference. That rather throws my calculations into kilter.