If you guys think flashback inside the vehicle is bad now, these things came out during a time where there was no such thing (coplite is an exception) as a flash shield around dash lights and deck lights. While windshields might not have been as curved, they still weren't straight up and down. I've seen this particular product used as both a rear deck and a front headliner mounted device. Because they are inherently "dumb / remote", sometimes the three or four lamp model was used with a clear light as a takedown.
The deckblaster from code 3 and the single dashmaster from Whelen technically had flashback shields close to this time frame (a bit later) but neither was incredibly effective. The deckblaster actually had a function where the halogen one allowed you to flip the colored lens down and use it as a front scene light or take down. Even as late as the dashmiser models (replaced dashmaster) with a takedowns were common without the use of a flashback shield.
I'm not sure these federal directors were technically bright enough to be used as a California steady burn (35w, I suppose you could swap in a 50w but I'm not sure if it would melt the filter), but I've definitely seen a setup where there was a flashing blue and a steady red in a two-lamp model to the front and a three or four lamp model to the rear that was red, amber, and blue set up as a traditional California setup. Regardless, the director series (the federal signal product pictured here) was actually a pretty interesting idea. Utilizing existing reflectors and filters it was a solid entry into the halogen dash and deck light market. I think it just ended up being a little bit too to bulky by the end of its tenure.
I used to have a full set of these and I wish I hadn't sold them. Cool items, thanks for posting l.