“Wooden box found at a thrift store. The area behind each keyhole is drilled out, but they don’t connect behind the metal plate.”
Answer: “This is apparently a manual dexterity evaluation test used in neuropsych to evaluate fine motor skills. The random keyholes are intentional to require different approaches to inserting the key and rotating it. There would have been 25 little metal keys stored in the wooden bowl part of the thing.”
Could it be the picture is upside-down?
"Tastes like lime..." I'm more concerned that the person would taste something that they don't know what it is (the answer is probably correct but still...)