Hot stamp coding is the oldest and most prevalent method of applying a code to a label, originating in the pharmeceutical industry. Brass type are loaded into the typeholder, which heats up. A temperature controller regulates the heat. The Coder uses a ribbon which has ink and resin bonded together. When the label stops a signal is sent to the coder which activates a pneumatic solenoid to fire the typehead out. The brass type press against the ribbon and then against the label. The force of this leaves an impression in the paper and the ink from the ribbon in that impression.
The code is immediately dry, so no smudges will occur, and no one can remove the code without defacing the label so this code is the most tamper-proof. The downside is that the holder gets hot, and so changing codes means either purchasing a second typeholder to load the new code in, or allowing the holder to cool before changing the code. For simple date codes the new code can be loaded in the morning and then the coder is turned on. A roll of ribbon can provide several thousand codes so the cost of a code is a fraction of a cent.