The newly found programmes - which introduce the character of Alistair Lethbridge-Stewart, better known to audiences as The Brigadier - will be available on iTunes from today and will later come out on DVD.
Phillip Morris, the director of Television International Enterprises Archive, unearthed the programmes by looking up the records of overseas shipments of tapes made by the BBC.
The stories, The Enemy Of The World (1967) and The Web Of Fear (1968) and both starring Patrick Troughton as the second Doctor, have now been remastered by BBC Worldwide, the corporation's commercial arm.
More top news
The Duke of Cambridge said his children were beginning a "lifetime of friendship" with Canada as they began their tour of the country.
When and where are they on, and how do they work?
What better, more dramatic spectacle has there ever been on American television?