Buffalo Nickels: Date on coins?

1Bufffan

Do you know How the Dates were placed on the coin die, cut into the master? did they have to use a four digit logotype, did they ever have to punch a die separately after it was made? not much is known about the Die Shop at the Philadelphia Mint I guess they did not want the public to know about their operations. It seems on some coins that the #19 was already on the Master Die and it seems that the last two digits were added by punching the Die later on what is your thought on this? Thanks in advance for your answers.