The principle differences is in the type of cab fitted, four at least to my knowledge. The earlier ones had wire mesh grills in the side panels of the hoods top and bottom, the later ones had louvres on the top only. The first ones were provided to the British army in North Africa, as well as the mesh side panels they originally had an American type of cab, basically box shaped without the chamfered sides. These followed the British army to Italy where the cabs were cut down and the roof edges chamfered to fit the loading gauge. More were produced in readiness for the D-Day landings, these had a cab similar to the 'cut down' cab and the louvred side panels. The next variation was with an even further lowered cab with the cab roof flush with the hoods. This was achieved by moving the air compressor from beneath the cab floor to a box on the running plate ahead of the cab. After the war the only ones to remain in the UK was the pair from the original batch used on the Longmore Military Railway, they were out of use by the mid 60's. A few went into industrial use in France one of which is preserved but the biggest user was the Italian Railways were the last ones were withdrawn only this century, although they had been re-engined twice, the second time with a single engine more powerful than the two Buda engines originally fitted.