I have a pre-ban Colt Sporter Target with a mismatched serial #.  The early 90's sporter serial #s are prefixed with the model type. ST for the Target, MH for the Match HBAR, NL for the 9mm lightweight, SL for the Sporter Lightweight, and CH for the Comp HBAR.  My rifle is marked "Sporter Target" but it has an MH prefixed serial #.  How rare is this mix up from the factory and does it add any value to the rifle?  

Did you buy the rilfe new, or used?

New. I actually worked at the shop and we got 7 in so I went in the back to select my serial # and found the mismatched one...so of course that's the one I took.  The box reflects the mix up as well.  Here's the kicker....I only paid 609.00 for it!!

I think you need to return it ASAP to the Factory so they can fix their records.  I'm sure they'll appreciate it.