I've recently acquired a Regal one-row melodeon in G, dating, I think, from the late 1920s. At any rate, the closest image to it that I've been able to find comes from an old Honer cataloque:
At the moment, the treble side plays adequately , if somewhat wheezily, while the bass end is very quiet indeed. It has various obvious problems - leaking bellows, at least one valve issue on the treble side, and the leaky bass end. The plan is to try and restore it to full playing condition, if I can.
As you see, it has three stops on the treble side, and two basses.
Most of the Regal one-rows that I've seen are black - this one is finished in a reddish-brown. The corners are protected with nickel-plated tin, stamped "Regal. Made in Germany". As I understand it, Regal were made by Hohner as budget instruments, and the time and effort involved in restoring this one will probably not be justified financially. But I hope it will be interesting.