While we might not know all stories behind additional numbers it has been discovered that in later years LEGO usep numbers to designate the mould they are using. With massive productions moulds tend to wear out and need to be replaced. This case is well known with basic 2 x 4 brick aka. 3001, which are produced in large amounts. Latest numbers embeded on the bottom of the brick are 200+.

While we might not know all stories behind additional numbers it has been discovered that in later years LEGO use numbers to designate the mould they are using. With massive productions moulds tend to wear out and need to be replaced. This case is well known with basic 2 x 4 brick aka. 3001, which are produced in large amounts. Latest numbers embeded on the bottom of the brick are 200+.