When I was younger, and what I heard from my mother, so my information is from about 1940's in Brooklyn, you trusted the proprietor of a food establishment to police himself. You were relying on his yiras shomaym and knowledge of halacha.
the corner luncheonette, the butcher, the takeout place.
It was only as establishments wanted to service customers that didn't know them that formal hashgachas became so established.
So I guess I'm disagreeing with the premise of that Kol Koreh.
And so it was for thousands of years before that point in time.
You know the famous story of the Bal Shemtov when he traveled to a small town and got to a small inn owned by a simple Jew.
The yid offered him a beautiful meal fit for a Rebbe even though it was much more than he could afford to offer, but the Bal Shemtov threw the food on the floor in a rage when he found out the yid wasn't under the OU.
