There were Lister Engines and Petter Engines. The companies later merged. Production was in and and around Druery England until the 1980's. Petters and Listers were built new in India under license for a decade or two. Now it's a free for all with Listeroids and Petteroids built in backyard shops in India. Quality varies. Parts are reasonable easy to come by on ebay. Old Listers and Petters are common as dirt and now sold for scrap metal prices in the British empire. I have a 1970's or 1980's "Krysler" brand petteroid which is a PHW1 Petter. It used to have a serial number plate but the previous Amish owner chucked it in the junk.