The Major Diatonic Harmonica was originally intended for playing simple Folk music of the nineteenth century and its notation layout was adequate for that purpose. The Major Diatonic harmonica is the most commonly used tuning for playing Blues, Rock, Country Folk & Jazz.
Several other manufacturers, using various names stamped on their cover plates, for marketing purposes, have the exact same notation layout as a Lee Oskar Major Diatonic harmonica.
The original style of playing, known as 1st Position (Straight Harp), is suitable for playing simple melodies, Folk music and various other types of music that call for melody lines, along with some chords. 1st Position (Straight Harp), is still used by many players today, but due to its simplicity of sound, it is not as popular as 2nd Position (Cross Harp).