A few posts back we looked at missing episode reconstructions and the use of 'telesnaps', together with surviving audio soundtracks, to rebuild lost episodes.
Audio soundtracks exist for all the missing stories, which have now also all been released on CD with supporting narration.
Telesnaps exist for the majority, but not all, missing episodes. No original telesnaps are known to exist for the first Doctor stories The Reign of Terror, Galaxy 4, The Myth Makers, Dalek Masterplan, The Massacre, or for the later second Doctor stories The Invasion and the The Space Pirates.
Some stories are incomplete - no telesnaps are known to exist for the fourth episode of Marco Polo, The Wall of Lies, although records indicate that they were taken. Telesnaps aren’t known to exist for the fourth episode of The Enemy of the World.
Many telesnaps were published in Doctor Who Magazine (DWM), and their Classic Comics (DWCC) spin off magazine, and also appear on the Beeb's classic series website in the photonovel format (here).
Marco Polo - DWM 342 – 347 (missing Episode 4)
The Reign of Terror - no telesnaps surivive
The Crusade - DWM 280 and BBC Website
Galaxy 4 - no telesnaps surivive
Mission to the Unknown - no telesnaps surivive
The Myth Makers - no telesnaps surivive
The Daleks' Master Plan - no telesnaps surivive (remade for Episode 2, on BBC Website)
The Massacre - no telesnaps surivive
The Celestial Toymaker - no telesnaps surivive for episodes 1-3
The Savages - BBC Website
The Smugglers - DWM 217 and BBC Website
The Tenth Planet - DWM 207
The Power of the Daleks - BBC Website
The Highlanders - DWM 233 – 236 and BBC Website
The Underwater Menace - DWM 220 – 223 and BBC Website
The Moonbase - BBC Website
The Macra Terror - DWM 251 – 254 and BBC Website
The Faceless Ones - DWM 260 – 264, 266 and BBC Website
The Evil of the Daleks - DWM 237 – 243 and BBC Website
The Abominable Snowman - DWM 224 – 229 and BBC Website
The Ice Warriors - DWCC 24 – 26, DWM 217 – 219 and BBC Website
The Enemy of the World - DWM 273 – 277 and BBC Website (missing Episode 4)
The Web of Fear - DWCC 18 – 20, DWM 211 – 213 and BBC Website
Fury from the Deep - DWCC 15 – 17, DWM 208 – 210 and BBC Website
The Wheel in Space - DWCC 21 – 23, DWM 214 – 216 and BBC Website
The Invasion - no telesnaps surivive
The Space Pirates - no telesnaps surivive
There's an excellent detailed article on Who telesnaps here.