Its a plug in device - basically a glorified floor standing lamp, connected via an IEC 60320 C14 chassis mounted inlet - not a fixed installation, so I doubt the NEC even applies.
The USA is a mess for appliance safety standards, but as its in the public area of a workplace, I bet OSHA wouldn't like it if an inspector saw it.
We never got to see the finished wiring in the large box, but assuming that the lid was secured so that tools would be required to remove it (and a cable tie through a drilled hole at each corner would suffice), and physical separation of low voltage control circuit and mains wiring was adequate, the only notable flaws would be failure to ground the metal toggle switch, and lack of grommets on the cable holes. Also, crimps, wire nuts or Wago connectors should have been used for the mains wiring in the traffic light rather than lapped solder joints.
It *should* be fused - we didn't get to see if there was an inline fuse. IMHO a fused C14 inlet should have been used.
If I was tackling that project, I'd mount all the SSRS on a grounded metal plate inside the traffic light, with the common wire of the low voltage side grounded, put an inline fuseholder inside the traffic light, use a UL approved inline switch in the cord to the light, and put the Arduino and optoisolator board that connects to the matrix inside the pinball cabinet, powered by an isolated DC-DC converter so there are no issues with ground loops.