The two letters are in different handwriting though on the same stationery. The one linked by Bodad is pretty surely not written by Leadbelly though presumably dictated by him. The other looks like Leadbelly's hand to me (the one in an auction), though the repro is a little dim for my one good eye. The "H" in this is Leadbelly's, and he seems to capitalize "H," "B," and "P" regularly, as Huddie did in all the specimens I've seen.

There are two Oak publications from the 60s, "The Leadbelly Songbook" and "Folksinger's Guide to the 12-String Guitar as Played by Leadbelly." The latter reproduces a memo, unsigned, in which Huddie says "Because don't forget Because there is a Book writing About my Life and i dont think ofent [?] That Book The Book was any way Bobry [?] of of [sic] my Life Because Lomax did not rite nothing Like I told Him."

The songbook includes a photo of Huddie and Martha on p 6, and under it is an inscription "Lisen folks this Leadbelly talking to you How do you do." On p 18 is a letter to Moses Asch, on Astoria Hotel stationery, dated 12/6/1946. There's no signature but it begins "Dear Mr Moe Ash How do you do this is Your friend H.M. Ledbetter righting." All three of these items are in the same hand, and it looks like the one in the auction letter.