The model breaks are as follows.
1978 VB 250 starts at 73M11841 (1600 produced)
1979 VE 250 starts at 73M13468 (1400 produced)
1980 VF 250 starts at 73M14298 (600 produced)
1981 VG 250 starts at 73M15939 (unknown)
If you add the produced numbers on to the starting model numbers, it will not add up.
I cannot account for this, maybe someone has some ideas. (maybe overlapping models?)
The above starting serial numbers were taken from the Montesa parts books for the various models.
Your serial number is 73M15620
Clearly a late production 1980 VF 250
Honda red frame, greenish/gold forks, (same colour clamps) Corte Cosso shocks, yellow plastic tank.