The heart of the Anglo system consists of two 10-button rows, each of which produces a diatonic major scale in a pattern devised around 1826 by Bohemian designer Joseph Richter for use in a harmonica (Richter tuning). An advantage of the Richter tuning is that pressing three adjacent notes in one row produces a major triad.
Also, because the travel direction inverts as you progress up the scale, at the point where the scale crosses from one side of the concertina to the other octaves can be played in the home keys.
Initially the term Anglo-German only applied to concertinas of this type built in England, but as German manufacturers adopted some of these techniques, the term came to apply to all concertinas that used Uhlig's 20-button system.
Use of the "German" part of the title Anglo-German ceased in the UK during World War I. For example, if the row closest to the player's wrist is in the key of G, the next outer row is in the key of C below.
It was developed in 18 by Sir Charles Wheatstone of Wheatstone bridge fame after several years of building prototypes, a few of which still exist (in 1829 he patented its direct predecessor, the Symphonium, but he did not actually patent the concertina itself until 1844).
2 HISTORY The concertina belongs to a class of instruments known as Free Reed instruments, which also includes accordions and harmonicas.
It hasn't been played for over 50 years but still seems in decent working order with a rosewood box. The overall condition is used but good I would say.
It became popular with music hall performers, several of whom, such as Percy Honri (who billed himself as "A concert-in-a turn") and "Professor" J. Mac Cann, were musicians of the highest virtuosity.
In due course other firms such as Lachenal and Jeffries were founded (several by ex-Wheatstone employees) the cost of concertinas lowered, and the instrument moved out of the drawing room and into the world of popular music.
Please e-mail me with any corrections, additions and comments. My partner in crime, Anne Gregson, plays the English.
I would welcome any information from players elsewhere in the world that I can incorporate into later versions.