All the major castings share common fixings, so the motor could be original, modified or a mix'n match of unrelated parts. The engine number denotes type and a guide to model year. Frame and engine numbers do not match.
Crankcase castings for A7 500cc motors and A10 650cc are the same, just the engine number prefix differs, so unlimited scope for what's inside.
Barrel/Jug can be distinguished by the number of fins. A7 has 7, A10 its 8.
Along with the barrel, it's inside where the parts are specific for the capacity. Cranks, rods, pistons and of course the head casting and valves. The rest of the bits, such as oilpump, drive train, timing gears are all the same.
Swarfy.