The second set was Lost in Time - Collection of Rare Episodes, featuring eighteen episodes from twelve otherwise incomplete and missing stories of the First and Second Doctors' tenure, in addition to various surviving clips, censor trims, and off-air footage. Two stories, "The Crusade" and "The Moon Base," are presented as complete by including the soundtrack for their missing episodes.
I bought Lost in Time knowing it would be a simultaneously interesting yet frustrating experience: some episodes have a beginning but no closure, others present only a conclusion with nothing preceding it, and some are just smack in the middle of a story with no explanation of what's going on or what will happen. But unlike one particular moron on Amazon complaining over incompleteness, I knew this would be exactly the case.
Doesn't make it any less difficult when you're actually watching them...
It's not so bad watching only episodes 2, 5 and 10 (out of twelve) of "The Daleks' Master Plan," which from what I've read seemed to be a rather convoluted sequence of chases strung together. It is irritating though when seeing episodes 1 and 3 (out of six) of "The Faceless Ones," since it turns out to be a rather interesting and gripping story about disappearing people and sinister alien agents at an airport. Much the same with episode 2 (out of six) of "The Abominable Snowmen" and episode 1 (out of six) of "The Web of Fear," the show's two Yeti stories.
The worst is having only episode 2 (out of seven) of "The Evil of the Daleks," easily the best Dalek story the show's ever done and there's just this tiny piece of it left.

So it looks like I'll be tracking down some of those complete story audio CDs that the BBC's put out in the last few years.
Something particularly interesting are the brief off-air clips, shot by fans pointing silent 8mm film cameras at the TV screen, synchronized with the relevant audio from the particular scenes; they have this strange distant, ghostly quality...
One of the other reasons for getting the set beyond my interest and curiosity with the subject was because compared to the other incarnations of the character, Patrick Troughton's Second Doctor is the one I'm the least familiar with. Since only six stories still exist in complete form, I ended up missing them back when the show was played on PBS in the 1990s. But after watching these surviving episodes along with "The Tomb of the Cybermen," I've really warmed up to his characterization, and look forward to collecting more of his stories, particularly "The Invasion."