Dating A Lachenal From The Serial Number in Concertina History Posted July 3, 2019 On 7/2/2019 at 4:20 PM, stewbob said: Hi, Does anyone know what date roughly my Lachenal concertina is please? It has a serial/model number of 85842. It's a 31 button model.. Thanks for your help thanks for the info - 1885 - wow.. not sure how i can tell the difference between steel and brass reeds? don't know anything about these instruments.