Maybe special order vs off the shelf (and then receiving its own ID)?If the lightbar mounted on Squad 51 is a CTS you need to reconsider your date of introduction of 1973- the pilot episode was filmed in the fall of 1971.
I'll look into this as I get time. Maybe my local library can do an transfer, otherwise Berkeley and Sacramento are about 2 hours away, so not out of the question.If anyone lives in California and can access a library. The "California Department of the California Highway Patrol " published a book in 1973 called "Twinsonic Light Study" It can be found at the following library:
San Diego State University
University of California, LA
California State Library, Sacramento
University of California, Santa Barbara
Stanford University Libraries
UC Berkley Libraries
University of California, Richmond, Northern Regional Library
Might have some interesting information and history in it.