Until the introduction of the Golden Melody in 1974, unless the diatonic harmonica were solo tuned like the long discontinued Marine Band Soloist/School Band models or the present day 364S, ALL diatonics being made, the tuning right out of the box was in 7 limit just intonation. 19 Limit is more versatile in terms of positions, but ALL diatonic recordings made until 1974, there wasn’t a choice and they’e all in 7LJI. Hohner began using 19LJI in 1985 and stopped using just intonation in 1992 and settled on three different compromise tunings that are still being used to this day but the GM have still bee tuned to ET since its introduction.