The 4 digit system was introduced by Lionel in 1970. The second digit indicated what year it was made, but this was only for locomotives. For example, the 783 Hudson was item 8406, meaning it was made in 1984.
It wasn't until 1987 when Lionel was purchased by Richard Kughn that the 5 digit system was born. This requires a bit of memorizing to understand what product has which series of numbering. For example, collector line cabooses were normally in the 17600 and 19700 series, and big steam was in the 18000 series. Eventually these had to be changed as more product was being made.
In terms of boxes, Joe Stachler did a very thorough view of modern era Lionel boxes. Though for the most part, MPC boxes were white, though later ones used the retro orange and blue boxes.
LTI collector line equipment typically used the same orange and blue, whereas the traditional line product from 1988 to 1992 came in sharp black and white boxes.