Is there a good and easy way to tell an original and a reproduction duckbill flash hider apart?  How difficult are originals to come by, and what is the current going price?  Thanks.

A very nice Original will run you $125-$175, repros are pretty easy to ID compared to originals and some are even marked.

I will have to disagree Hip,, the old "made from scratch" 45bravo ones were a dead ringer to originals, and the ones innovated industries are making a real good repro.. The ones Sven made looked good and are marked with the M.
Many repros started life as regular 3 prongs and are modified. THOSE are easy to spot.

In my searching for the muzzle device addition to the Retro Barrel Spreadsheet, I know Innovative Ind. claims to be spot on dimensionally.
I can also confirm that the Manticore ones are marked with an M on the flat that butts up to the shoulder. Innovative Industries does also appear to mark their copies in the same way, at least from the comparison to Colt pictures they show on their website. It looks to be an "I I" on the back.

Your quite right, I didn't even think of the turn downs and such.... I was more concerned about difference between originals and repro, and giving him a price range. Thanks for the additional information.