I have searched all 70 “Trick” Lock German patents-only 9 UK
and fewer Belgian and French, to no avail! The two nearest German were DE263175 & DE342316, by the inventive Damm & Ladwig firm.
The first proposes that a sliding shackle guide has to be depressed, after the key is turned, and the latter patent requires that, after turning the key, the sides if the body of the padlock have to be slid.
I think the unusual sequence of events may be the result of using a single ribbon spring to perform all tasks, the key slots being for show, as proposed by Tom Gordon. Is there a shiny portion at the bottom of the keyslots, or are the corners rounded? Can levers be seen within the keyhole. As Adrian Weber was not able to find a Burg or other lock, it may possibly be a cheaper, but attractively presented, lock.