I think it will take you awhile to get a feel for early guns, because there is just sooooo much variety in them. To me, you were lucky to not win it. The parts might be original, but the gun as a whole is not. The low price reflects the fact that it isn't an 18th century firearm.
The best thing to do is think hard about what type of early firearm you want the most, and then read, read, and read some more. Educate yourself on that particular style. Buy books, read articles, go to museums and study originals. Then when you see an auction you can get the most for your money, and be satisfied you now own a historic piece for your collection.
This of course is just my humble opinion. I'm not an expert, or claim to be, just a guy who loves historical arms like everyone else on this forum. Some might think this is an original piece. That's the benefit of a site like this, you get both sides of the argument, and you get to make the best decision based on what you believe.