The little engine that could...or maybe could not?

My OO gauge Sentinel Y3 model arrived from Model Rail Magazine (9th Aug 2011) as pictured.

MRM (Dapol) Y3
(with a distracting back-drop from another interesting book I've found lately)

The supplied instruction sheet set me wondering due to the comment that the model was produced from detail obtained from Isebrook at Quainton road.

Extract from instruction sheet

However, Isebrook is a single geared type as with the Y1!

Isebrook's chains drive from the crankshaft sprockets

So is the model actually a Y1 or Y3? I'll leave it to you to figure out; this posting might help. In reality, it's not important; it is a fine, tiny model which runs very nicely. For more information have a look at the Model Rail Magazine's website.

Here is a small video of Isebrook in preserved action on YouTube at the Buckinghamshire Railway Centre, Quainton Road. The occasion was the Sentinel Drivers' Club 'Noggin & Natter' held on 10th April 2011.