Jacob Charles Jeffries, known as Charles. Considered to be the best maker of the Anglo concertina but also invented the rarely seen Jeffries Duet System and made other concertinas including English and even Maccann system duets.
Charles was never trained, nor did he work for other makers and appears to be entirely self taught. It seems he was apprenticed as Brushmaker and brushmaking tended to be itinerant so Charles travelled a good deal.
He sold concertinas on his travels and these were likely to have been made by John Crabb. Later he stopped travelling and manufactured concertinas himself. There is a possibility that some unmarked Crabbs were sold as Jeffries in the early days.