Craig Bierko wears an unidentified watch

Late in The Thirteenth Floor, Douglas Hall crosses a wet downtown street in 1937, a fedora in one hand and a folded overcoat over the other arm, dressed in the three-piece suit of a man who belongs there. He does not. The street is a simulation his own company built, a block of Los Angeles run on software, its citizens written to believe they are alive. Craig Bierko plays Hall, a computer scientist who reaches that world by lying down in a machine and waking inside another man's body. Josef Rusnak's film opened in 1999, about two months after The Matrix, and it runs the same premise in a quieter register: a man who cannot tell whether the reality around him is the bottom of the stack or a level inside someone else's.

The idea was not new even then. The film follows Daniel Galouye's 1964 novel Simulacron-3, which Rainer Werner Fassbinder had already adapted for German television in 1973 as World on a Wire. Hall's mentor Hannon Fuller, the man who built the simulation, is murdered, and Hall becomes the prime suspect with no clear memory of the night. He goes down into 1937 to recover what Fuller hid there, and the further he descends the plainer it gets that his own 1999 is not the top level either.

The watch on Hall's wrist is the one object in the film that cannot be placed. No published source identifies it, and it is not legible in the available stills: in the 1937 street his left wrist is buried in the coat folded over his arm, and his right is bare to the cuff as he grips his hat. In a film about telling a real world from a copy, the instrument made to mark real time is the one detail no source can tie to anything real. The brand and model stay unknown.