If I'm looking at older HO Bachmann trains w/ boxes on eBay, how do I tell which box is an older Bachmann box? For instance, I see a lot of boxed loco's & train cars in a mostly white box w/ a weird font "B" within a circle. When were those Bachmann boxes produced? The reason I ask is that I want to buy a couple freight cars and maybe another loco to match my old Bachmann loco from the early 70's. So it would be useful to know what the boxes looked like in the 70's, 80's & 90's, etc. I assume the box design changed a little each decade or so? Thank you.