The Hohner Chromatica #261 was of the Chromatica series of harmonicas. It hasn't been produced by Hohner for many years. It was displayed in the Hohner catalog of 1971, but was discontinued shortly after that time. Of the 261, 262 and 263, only the 263 is produced today.
The Chromaticas #261, 262 and 263 were "glissando" chromatics. That is, the reeds were set in a position of adjacent half steps in a row (left to right-A, A#, B, C, etc., chromatic, without a slide button).
The #261 was an octave-tuned instrument, blow only. On an octave tuned harmonica, each hole has 2 reeds tuned 8 diatonic notes apart. Octave tuned harmonicas have increased loudness compared to the non-octave harmonicas. On an octave harp, the lower pitched reed boosts the amplitude (volume) of the upper reed in a hole.
The 261's first hole on the left(with a piano keyboard embossed on the cover) had two reeds: the low A in the bass clef and the high A of the bass clef. The range of the #261 was almost 3 octaves, A to G, 70 reeds. The hole farthest to the right had two G notes, one was the high G above the treble clef, and the other was the G above that.
By playing every other hole on the glissando chromatics, you could play major, or minor, or other music scales. The glissando harmonicas were originally designed for use in the harmonica orchestras popular in the 1930s and '40s, and became less popular as the decades progressed.
Other Chromaticas in the series included the #265 and #268 (both are 2-deck bass harmonicas), and the #267, a 48 chord harmonica. These three Chromaticas are still produced by Hohner, and copies are made by other harmonica manufacturers.
If you'd like to get a production date on your harmonica, it may not be possible, but an estimate can be made to within about 10 years. If the wood "comb" (sound chamber) has a "marbled" look on front, back and sides, it's probably one made between 1930 and 1938. Sometime after that, a solid color wood stain was used.
Check the harmonica's underside metal cover, the one with the words, "M. Hohner's Chromatica #261." Look at the center of the trademark logo, the part with the two hands holding a circle. Inside the circle, if there is a 6-pointed star, your harmonica was made from about 1930 to before 1938.
After 1937, the German government ordered the Hohner company to remove the 6-pointed star from the Hohner logo, claiming that it was a Jewish religious symbol-The Star of David. It actually commemorated the 6 officers of the Hohner company. After 1937 and to this day, the center of the circle in the trademark has no star. If your harmonica has no star, it may have been produced anywhere from 1937 to shortly after 1971.
Check the trademark again, but look at the circles with cities and Grand Prix medallion dates listed (Chicago, 1893; Philadelphia, 1926; Geneve(Geneva) 1927; Paris, 1937). The most recent medallion year listed will tell you that your harmonica was produced AFTER that date.
There is one interesting contradiction to the star dating. In the 1971 catalog, the Hohner Chromaticas all have the 6-pointed star in the photographs. Maybe they used old photographs of the Chromaticas. You can get an estimate of your harp's vintage by using all of the above check points to make an educated guess. The star in the logo is only one indication.