I am grateful to Russell Barnes for his generosity. He sent two letters, one from Red Nichols and one from Charles Beiderbecke (Bix's brother). You can see them by scrolling down in the page
The discographical information in Red Nichols's letter is of great interest. I invite readers to compare what Red tells us with what is listed in Rust Jazz Records Discography.
Charles Beiderbecke tells Ralph Venabkles that Leon Beiderbecke's middle name was Bix. Rich Johnson in his book "Bix, The Davenport Album" provides strong evidence in support of Leon's middle name being Bismark. I 'm with Rich.