Not only is the Solist rare, not only is it next to impossible to find one, but I have been unable to find further information about it, so thanks for your insights. It’s also hard to find much about the Professional, but at least there are references out there. Hohner must have made very few of these. It’s a shame. I’m sure now that they were made during the 1960s, quietly while all the advertising emphasis was on the popular models.
I remember The Lovin’ Spoonful and John Sebastian very well. I saw him interviewed in a documentary recently.