This reel mower has recently been donated to the Rural History Museum,
Ferrymead Heritage Park It's the second example I've come across and is basically two 16 inch model D's joined together.
As you can see in the attached photos, it users two side plates on each side and has a Briggs and Stratton engine.
Unfortunately the engine is missing the identification tag but probably dates from the late 1950's to the early 1960's.
The museum intends to straighten the handles, get the motor working and generally tidy it up before putting it on display.
Alan
