I was reading Louis Armstrong’s account about a Jewish family he knew when he was a kid. He worked for them, and they loaned him money to buy his first cornet. Here’s the quote of interest:
(The whole thing is a great read, BTW)
What the heck is “insurance oil”? Oil sold by some insurance company? Oil sometimes used in arson to collect insurance? Google has nothing, and only says current horn cleaning uses lukewarm water, dishwashing liquid, and a snake.