The B series indicates a more recent manufacture.They are both Mark IV revolvers and this is indicated on the revolvers. The no series,A and B series Mark IV revolvers are basically the same revolver with difference being confined to how old they are.
Why the difference in price? Because it is a silly world out there.So while a longer barreled A series revolver goes for less than a shorter barreled one,a longer barreled B series revolver goes for more than a shorter barreled B series revolver.Why? Because there are fewer long barreled B series revolvers
BTW both the small and large grips are inter changeable.
What can be sillier than a safety on a revolver,yet people pay more for one which has it.I have even seen a safety lever installed in a DAO CZ .25 pistol.
Perhaps it is rightly so.See the number of idiots who pose with their finger on the trigger? The vast majority,when they hold a firearm, instinctively do this in India.Probably on account of the limited exposure to firearms and ignorance of firearms safety.
Sorry for the rant.
Of all tyrannies, a tyranny exercised for the good of its victims may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end, for they do so with the approval of their consciences.