I too was disappointed in the detail on the signal and traffic signs in MP. They were correct for the period but things were just not right.
The ACME signal was red but, as mentioned, no STOP arm extended!
The diamond STOP sign was wrong, no detail, no nothing. Sad.
I would have been happy to provide photos or actual period signs for use or reproduction if they had only contacted me. Maybe next time,
www.caltrafficsigns.com