So I've come across this situation a few times. Someone will offer assistance on an airplane or something, and the flight attendants ask for proof... or in some foreign country, like when I went to Britain, I saw a US doctor trying to write an emergency Rx for himself for some beta blocker, and the pharmacist asked "Do you have a copy of your license?", and eventually dispensed his propranolol. Is there anything out there that "proves" you're somehow licensed? This probably isn't an issue for residents or academic physicians, who can probably flash their hospital ID with "MD" on it. Do you maybe get a card when you apply for a state license? A pocket-size metallic engraved trinket from the NBME for passing step 3??