That's the date that sticks in my mind too.
As I recall, JRRT wrote several versions (which are in the early HoME volumes),
including the prose version that is similar to what's in the 1977 Sil, up until
1937 when he set his First Age material aside to work on The Hobbit. He
then later went back and edited the prose account in the 50s, and that is the
basis for the version Christopher first published.
I'm going on memory and too busy to do much Googling on that (I'm Googling on
things for my day job now--pesky reference questions :-), so squire or someone
else correct me if I'm wrong or fill in the
details.
Tolkien, Page from the Book of Mazarbul
