Oh dear Longarm, ...... looks like you Monarch peeps dont know what you're flying!! The Monarch A300's are most certainly B4'S! Yes, you're correct to use the generalisation of A300-600, but the specific is A300B4-605R (G-MAJS/G-MONS/G-OJMR/G-MONR)
Oh, an i think the Air Scandics are A300B4-102's(?) and 203's