Good write up.

Back in the 2000s I used to buy silver / gold coins in P2P meetups. I would meet in busy coffee shops. Never had a problem.

Like you said you can quickly meet dedicated sellers and then your job is much easier because trust gets built.

For new purchases, I would bring a "Fisch Scale" (https://www.thefisch.com/) to check the coin was legit....never had a problem getting fake coins...but once I knew someone I wouldn't bring it in to coffee shop as I trusted them.

The seller I bought the most from would scavenge estate sales looking for old coin collections. The other guy I bought from was actually a police officer (almost spit my coffee out when he told me that), had no idea where he was getting gold coins from and didn't want to ask...