Early engine, what model?

I would suggest that the s/n that you have supplied are not correct, my Feb 1969 20M3 Commando is 130XXX and they shifted the points to the end of the cam shortly after.

209031 indicates 1972 manufacture. 

engine is 20M3 series. so 68, 69, fastback early 70.

Not enough frame seen to determine any further. Center stand type may give a hint if original. Coil mount hints of 71+

It would be good to see a clear picture of the engine number.....

The gearbox number (across the top mount) would also be of interest.

Engine and frame numbers exactly 3000 apart?

And unless someone knows better, there's no (normal, or dare I say it, legit?) way that a 200000 series engine has points on the back of the timing case (and what looks like a blanking plate where the rev-counter drive would go on a 20M3 engine).

Could someone have mated a later l/h crankcase half with an early r/h half?

Engine number appears to have been restamped, head is also wrong if it is an early engine.

As I said earlier that both halves of that engine are for a  20M3(edit: remove S) engine . 200000 series has a 1x4" flat tab where the SN goes AND  similar flat tab under the timing side timing cover.

Of course different jurisdictions have different rules but for us the Frame/VIN/SN is the only thing that matters. Having an earlier engine is of no particular concern...and certainly not worth trying to fake a wrong  series number.