Agatha wanted to purchase ✣ one in the Black Market in Paris while searching for Dio Zardilev.
Possibly relevant outside information[]
Peter Henlein (1484-1542) was a German clockmaker.
Robert A. Heinlein's short story "By His Bootstraps" is about a person wound up in a time loop. Heinlein also wrote a novella, Tunnel in the Sky, involving a teleportation doorway.