One thing, but not the only thing, to consider is unified treaties on global standardization for IDs have thumb, hand & face prints on same IDs.
The Bible tells us "666" (Mark of the Beast) is a human number.
A human number is a biometric number calculated off of characteristics (thumb, hand, eye & face prints) individual to each person.
So the "character" (Mark of the Beast) on the right hand or forehead will likely contain biometric data of the person to whom it's attached or implanted, along with the possibility of the person's financial data, civic history, education, employment, bank account, assets, etc.