Starting a gas tractor

Would you confirm what your serial number is?

If it has four spark plugs, it's a gas engine. The spark plugs are those porcelain peices connected by rubber covered wires to the distributor cap. If it does not have four spark plugs, it might be a diesel. It will have three metal tubes going up to the side of the cylinder head that connect to a device called the fuel injection pump. To reduce richness on a gas engine, you open up the choke after it's been running a while. With a diesel, you usually just have to wait til it gets up to running temperature. Then the smoke should almost dissappear. Make sure you have antifreeze in the radiator and engine oil in the crankcase. The fuel tank should have gasoline in it if it has a gas engine. It should have No 1 or No 2 diesel fuel in it if it has a diesel engine. It's very important to keep everything clean and replace filters on a regular basis, as the owner's book would suggest.

As for identification, the number you gave is just a casting number. The actual serial number is stamped into the left side of the clutch housing where it meets the engine. There is a picture below. Note that a gas Dexta has a serial number starting with 959E... The diesel would start with 957E...
There were so few petrol (gas) engined Dextas that there is little known about production. It is probably a 1959 model. If someone was fooling around, it is possible that they could have put a Massey Ferguson 3 cylinder Perkins gas engine into a Dexta chassis, but why do that? Some farm mechanics could have converted gas to diesel and visa versa.