I used to work with an engineer who took all of his notes in mirror-image
longhand, so clients couldn't read over his shoulder in meetings without
being obvious. He said he learned the trick "from an old Italian"
(meaning DaVinci--he wrote his notebooks in mirror image).
Seriously, though, I never proofed cold or hot metal type any other way
than in reverse, but people who didn't mind cleaning the type would ink
it & make a proof impression to check. Watch those b's, p's, q's, and
Ink Spot Printing & Copy Center, Inc.