After a discussion on another forum, I realised these letters are useful because they help prove that Martin did not steal his pen-name from J.R.R. Tolkien (a fairly ridiculous but nevertheless persistent claim in some quarters). Thusly:
Martin was confirmed after he turned 13, between September 1961 and 1962. He took the second 'R' of his name as his confirmation name,
as confirmed on his own website.
In the letter published in
Fantastic Four #20 (dated November 1963, probably actually on shelves 1-2 months earlier due to Marvel's cover-dating policies), GRRM is clearly not used to using the second 'R', as he is calling himself 'George R. Martin' at this point. However, by
Avengers #12 (January 1965 but possibly published in November 1964) he's calling himself 'George R.R. Martin'.
From 'The Heirs of Turtle Castle' in
Dreamsongs, GRRM states that he was unfamiliar with Tolkien until he read the pirated Ace Edition of
The Lord of the Rings. The Ace Edition of the novel was published in the traditional three volumes, with
The Fellowship of the Ring appearing in 'Spring 1965' and
The Two Towers in early July 1965. In the same essay, GRRM points out that he had to wait patiently for the next volume to appear, which means we can date his first encounter with Tolkien to a fairly narrow timeframe in early 1965 between the publication of the first two books, four years after he took the second 'R' of his name and a good six months after we have proof that he had already started to use the name 'George R.R. Martin' in correspondence
Edited by Werthead, 12 December 2011 - 04:31 PM.