Would this partial omission be attributed to grease?

@AUandAG said:
PS: do they still use grease at the mint?

Modern high-speed, high-pressure coin presses would not last long if they were not lubricated. So yes, some kind of industrial grease still needs to be used.

We sometimes get the wrong idea when talking about this "grease", as if it was the same brownish slimy stuff used in car doors. I've often heard people say "if it's just grease, why doesn't it simply squirt out?". But this kind of "normal" grease would be useless in a high-speed coin press; it would liquefy or even evaporate at the temperatures and pressures experienced.

It's my understanding that the mints generally don't use off-the-shelf industrial grease, but instead formulate their own in-house, specifically designed for optimal performance under standard operating conditions.

The industrial grease used by Mints worldwide is normally a solid or near-solid at room temperature; it melts and lubricates while in contact with the high temperatures that coin presses operate at. And while it does "flow like grease" when it's warm, clean and fresh, in use it quickly accumulates lots of microscopic particles of metal. When this old contaminated grease cools to room temperature, it becomes rock hard, and it looks metallic so it's hard to see on visual inspection of a die. This is the "grease" that causes grease-filled dies.

@jesbroken said:
Just out of curiosity, how is the lubricant applied during the striking process?
Jim

It's my understanding that a modern industrial high-speed coining press is essentially self-lubricating; you put the lubricant blocks in and the computers controlling the press decide when, where, and how much grease is needed. An engineer with a hot grease gun would only need to step in if things went wrong.