Are you a Robert Johnson obsessive? Musicologist Nick Dellow remastered a clean test pressing of Crossroads Blues. This is one of the cleanest recordings of Johnson I’ve ever heard.
Mr. Dellow seems to specialize in finding amazing things. Here’s an photo he uncovered taken in 1931 of McKinney's Cotton Pickers at the Pla-Mor Ballroom in Kansas City:

More Dellow goodness: An interview Brian Rust, with the creator of the Jazz Records 1897-1942.