Hello,
        I was wondering how or if there was a way to tell when a Bachmann train was made by the box that it is in, like TYCO has the Blue box (1950s), Red box (1960s) and Brown box (1970s).  Especially the trains that came in sets that were individually boxed inside the main set box.  These boxes don't seem to have any numbers or date on them.  How do you look at the engine or cars and tell how old they are?
I was trying to find any post on this but I couldn't.
  If this topic was already covered could someone link it to me please.

Hello, I am new to here and to HO trains.  I had some sets when I was younger, but nothing but just a couple of trains and a track.  The other day I dug out my old trains and some stuff that's been pasted down to me and I want to build a layout.  
Anyways I wanted to ask this question, I have a Bachmann Bicentennial set that has never been opened, and I was thinking about using it but I have no clue what it's worth and I hate to ruin the value by opening it.  I been doing web searches and can find nothing to compare it too.  Ebay has some used cars but that's about it.  What scared me was that I seen a BACHMANN THOMAS JEFFERSON BICENTENNIAL 51' BOX CAR - N SCALE #5205 for $698.75 on Amazon, and yea that is N scale. So back to the question should I open it or not.
BTW, I also got Tyco's, Alco 430 Diesel in Spirit of '76 and the Twin F9 Diesels Spirit of '76 plus some Commemorative State box cars.  Just another reason I wanted to open it.