Your Doll steam engine is not a 343/1 with an oscillating cylinder, but probably a 348/2 with a fixed cylinder. In any case, it is a machine from the 348 series. You can find out the exact model by comparing the dimensions of the base plate, the boiler length and diameter, the flywheel diameter and the cylinder shell diameter with the information on Ventix Pages. The existing fittings also help with identification. I am very sure that your machine is a 348/2, but I do not know the exact dimensions.