oh but life was so simple (in your dreems )if there was something so simple as an i/d plate i would not have wasted my time or yours by asking this question,but thanks for info on workshop manual kieron
MD2 ID plate is on starboard side of engine (left hand side looking on flywheel) and has almost always been painted over in my experience. (I speak as the owner, after removing a good deal of paint from said plate, of MD2 no 5420!)
Now, yer MD2 has the old type Volvo gearbox with ahead and astern cone clutches i.e. the shaft actually moves forwards and backwards, and the gearbox housing is cylindrical.
Yer MD2 also has a Dynastart, i.e. the flywheel is grooved for two belts for the Dynastart rather than toothed for a Bendix drive as in yer MD2B.
It's rather more confusing than any of the replies so far have suggested. Basically, the MD2 was 890cc, and the MD2B had a bigger bore, making it 1120cc and more powerful. The MD2B was available with either dynastart or an alternator, and with either the RB or MS gearboxes. If it helps, you can see the original product literature on the Volvo Penta website. The 1964 MD2 brochure (15.5hp) is here, the 1970 MD2 brochure (16.5hp) is here, the 1974 MD2B (23hp) brochure is here, and then there's another 1974 MD2B (25hp) brochure here. Make what you will of that lot!
Judging from those diagrams the easy way to tell is from the Oil fillers on the top. The MD2B has it central on each rocker cover (if that's the right term) whereas the MD2 appears to have it off centre