Hello wce and Jack Jack is correct ,the rear wheels are larger on the back of the Fastcut mower (most likely the same as the rear wheels on the Sunbeam Lawnkeeper)
I don't think wce's is a earlier version ,I can see evidence of the secondary skirt on his mower. I've had a few Pope mowers and others where the secondary skirt is missing from rust or damage.
I think if there was a Fastcut that was earlier than the Lawnkeeper there would be different parts used on the Fastcut .
As we know the earliest Victa rotary mowers had swing back blades, Austral Villiers, there were a few mowers in the 1960s with a similar blade setup to the Fastcut.
Here are a couple of early patents showing the newer modifications to the bar blade.
Happy to be corrected but I haven't seen evidence of a earlier Fastcut.
Thanks Jack for all the info., the Sunbeam history is definitely a favorite.
The early Sunbeam twin-rotor electric is the best looking electric mower in my opinion.
