ME31D09 double drive 4 wheel truck, 31mm wheelbase, 9mm wheels.
Fits the following models amongst others:
Tramalan - TA14 Glasgow sand & sett, TA18 Sheffield standard, TA19 Rotherham single ended, TA20 Birmingham radial, TH1 Birney safety car
ABS - R401 Leeds Kipperbox, R403 Leeds ex Hull works
Keilkraft - Edinburgh standard
These are the ex-BEC trucks.