What is the difference between an egg roll and an imperial roll?

The only difference I find is that "regular" Egg Rolls (EggRolls) generally contain only one meat, such as Pork, Seafood, Chicken or Beef, etc.. While "Imperial" Egg Rolls (EggRolls) contain at least 2, and usually one is Seafood, then the other will be either Pork, Chicken or Beef, etc. One article I read awhile back, (can't seem to locate it right now), it stated "Imperial Egg Rolls were served only to members of the IMPERIAL Palace, while to plain rolls were created for the 'common' people to enjoy this treat..."