Thinking of selling my Pre-Ban Bushmaster XM15-E2S all original (well I do have M4 handguards on it, but have the original ones too!) 16" HBAR Carbine I bought right before the '94 ban took effect.

It's turning quite purple now, as I've heard Bushmasters sometimes do.

What causes the purpleing and how much does it affect the value?  

Can't find many for sale to gauge the going rate.  What are some prices you are seeing out there and what's fair?  Or is it rare enough I should hang on to it?  

S/N is L059xxx.

Thanks!
James