Hornby Minitrix introduced the Blue Warship Class 42 - N206 Hermes - as one of two new locos at the end of their first year of marketing Minitrix models in 1973.  This model introduced the second generation of Warship to bear the Minitrix name - the buffer bar remained a part of the front and rear bogies, but the battery box now had a plastic, clip-in under tray rather than the metal casting of its first generation predecessor.  Basically, if you turn the loco upside down and there is a plastic moulding between the two bogies, then it is a 2nd generation Hornby Model.   These first two generations of blue Warship both had the Minitrix number 51-2034-00, or simply 2034

That does not preclude the possibility that Hornby sold off old 1st generation models when the blue Warship was first added to their catalogue.  I simply do not know if this happened.

In 1979, Hornby introduced a new design of Warship.  The buffer bars were not part of the bogies and the chassis was an entirely different design.  N208 had a green livery, but the chassis design was also adopted by the blue Hermes - which retained its Hornby N206 designation.  However it received a new Minitrix model number of 51-2942-00.

Many thanks to Jeremy for his photo from his own Minitrix Collection.