Ending June 16th, RR Auction has a typed, signed letter from Tolkien to Andrew Schiller dated June 22, 1957 (Chronology, p. 536) that discusses Sir Gawain and the Green Knight.

Letter link: Letter from J.R.R. Tolkien to Andrew Schiller • 22 June 1957 (#323)

In fine condition. Accompanied by the original mailing envelope.

Estimate: $3000+

https://www.rrauction.com/auctions/lot ... yped-letter-signed/?cat=0