These octave-tuned harmonicas are distinguished from the Echo Tremolo models by their curved shape. They have a wooden comb and come in four sizes; 28, 32, 40 and 48 reeds, as illustrated. The 28 and 32 models are available in the keys of C or G, and the 40 and 48 reed models in C only. However, the G in the 40 and 48 version is available as the Lieblinge brand .
For a book on the Tremolo harmonica see Tremolo & Octave Method by Phil Duncan in the books section