To overcome the problem of travelling over tarmac roads with tractors on steel lugged wheels, DARVIL manufactured these retractable strakes.
Loosen the bolts around the centre boss, drive forwards and the strakes expand out beyond the tyre depth. Lock the bolts and you've got extra traction. Reverse the proceedure to retract the strakes to drive on hard surface on the tyres.
The tractor is a 1945-51 Fordson E27N built in Dagenham England. E=England 27= 27 HP N=tractor. basically an improved Fordson model N. gas & vaporising oil engine with 3F-1R, optionals were electric starting & lighting, 3 point hitch & PTO.