Puzzle locks with exposed keyholes were widely used in ancient China and can be very tricky to open.
[1] There are three main types in China:[1] In Europe, many small puzzle padlocks had front plate with a face or mask.
The padlocks were designed to secure small bags or pouches and could be found across Europe with the most around the Danubian provinces and Aquileia.
[2] They were often shaped like rings and may have been fitted around the mouth of a bag as a sort of tamper-proof seal.
[3] The earliest Roman puzzle locks date back to the 2nd century BCE.