I just found a new and better source of what ATCO made after WW2:
http://www.oldlawnmowerclub.co.uk/mower/mower-listing

As you can see, they made 12" mowers until the early 1960s. The "typical illustration" of a 1950s version had the aluminium handles, but it had a short muffler. I no longer have any clear idea of when my ATCO 12" was made. If I hadn't sold it in about 1969, I'd look at the model plate and find out. If you have model identification plates on your mowers, the first 2 digits are the cutting width and the second two are the model year.

Last edited by grumpy; 10/03/12 09:57 AM. Reason: Add detail