PART 2/5 EXAMPLES:

Considered to be the earliest known public images In the early-mid 1800s. An underground European world of printers, decided to invent a genius way to hide erotic coitus images only seen using an Oil lantern or candlelight through the card.

So if you're wanting to hide something in the early 19th century and wanted to make some easy money, how about a deck of transparent playing cards to share with the guys with $$! These cards are considered Museum quality and are incredibly rare.