not a huge amount i'm afraid, so you may be disappointed.
its not that they are not great markers but some take strange barrels, and the price you can pick an a1 up for has depreciated these quite considerably.
I've seen them for £80 to £200 but I really think the £200 did not sell! so £80 - £140 it should sell. imho they are just as good/better than other markers in that price bracket slg, ion etc etc
hope this helps