Thanks. The earliest advertisement I've found for an anglo that could play in the key of D is from the 1850s, for a 22-button C/G.
http://books.google.com/books?id=SG4PAAAAYAAJ&pg=PA58&lpg=PA58&dq=%22improved+german+concertina%22&source=bl&ots=YDQyU42Fu-&sig=0mKosjOWSzUouoh5YulhDnWFTCU&hl=en&sa=X&ei=7gqDUNjcNKi40gGF_oC4Bw&ved=0CFoQ6AEwBg#v=onepage&q=%22improved%20german%20concertina%22&f=false
Theo, how often do you run across 22-button anglos?