Hi Gizmo,
I can advise that the first mower is an Atco - probably a 1952 model 17". The side plates are aluminium, which was a feature of the lightweight machines up until 1952/3. In 1954 the side plates were steel. The tank was as per the one in Deejay's first photo. The exhaust would have been of the pepper pot style. The clutch should be a cone style clutch. These machines replaced the earlier 17" mowers which were built between 1946 and 1952.
The second mower is not an Atco. It is an Austral Villiers which were made in Australia.
Cheers,
Sir Chook
