...may appreciate this link:
https://www.proz.com/kudoz/english_to_german/idioms_maxims_s...See his reference comment.
Side note:
Most languages listed on the Wiki page about "pig in a poke" use the image of a cat, 26 to be precise. Only six prefer "pig." In addition to English and Irish, that's Finnish and Estonian (which aren't part of the Indo-European language family), Swedish (possibly influenced by its neighbors, just as Hungarian might have been, since it's a Finno-Ugric language too) and Zulu (no clue why). All depends on the relevant target markets.
Additionally, if you need to "educate" your customers first, your entire argument goes down the toilet. The phrase will no longer be snappy or memorable, but time-consuming.
Not sure what Thomas thinks, but the German sounds trite these days; I wouldn't have used it in the first place.