Diaphragm gas meters of this type were invented in 1844. The design is basically unchanged to this day. https://books.google.com/books?id=RxcjAQAAIAAJ&pg=PA75

Diaphragm gas meters of this type were invented in 1844. The design is basically unchanged to this day. https://books.google.com/books?id=RxcjAQAAIAAJ&pg=PA75&lpg=PA75&dq=richards+groll+gas+meter&source=bl&ots=uTMnu4Qr6T&sig=I04YthTgywVsJVBgUqPrrmjnWSM&hl=en&sa=X&ved=0ahUKEwil-N_YlarKAhWBcD4KHWetBfkQ6AEIHjAA#v=onepage&q=richards%20groll%20gas%20meter&f=false https://books.google.com/books?id=RxcjAQAAIAAJ&pg=PA75&lpg=P... https://en.wikipedia.org/wiki/Gas_meter https://en.wikipedia.org/wiki/Gas_meter Too bad they don't look like this: http://www.gracesguide.co.uk/File:Im20100528Ed-Alder2.jpg http://www.gracesguide.co.uk/File:Im20100528Ed-Alder2.jpg