That is certainly a "Speedy", a model of the ex GWR outside cylinder pannier tanks built to haul the empy stocks from Paddington to Old Oak Common, 16 coaches uphill. A very powerful little engine but heavy with a red route classification because of the axleloading. I have driven quite a few of the 5" models and also fired and driven many miles on the only preserved example on the Severn Valley Railway. The 5" models prove to be reliable performers, easy to drive and fire and easy to maintain with all the valve gear outside. (Not like my Beyer Peacock!!).
Dave.