Speaking of ‘authentic looks’, I’ll share with you a lengthy story on California’s “manufacturer” plates and Shelby American. Just be certain you don't miss the last paragraph!
The absolute most definitive book (with photos, of course, of some of Shelby’s racecars) is the somewhat rare book called, “Daytona Cobra Coupes”. It was published in the mid-‘90s and copyrighted by Dave Friedman (Shelby’s official photographer) and Pete Brock (the Daytona’s designer who also worked for Shelby). I’m one of the lucky ones who owns a copy of the book (the ‘Limited Signature Edition’, with its own VIN plate, which is even more rare!).
A little background: Carroll’s businesses were twofold:
Car manufacturer - Shelby American
Auto dealer - High Performance Motors
Hence, Carroll was able to acquire both “manufacturer” and “dealer” plates from the California DMV. Carroll and a partner operated a car dealership, High Performance Motors, near the Los Angeles Airport (LAX) factory to where Shelby American moved after relocating from Venice, California. As a result of both businesses, Carroll would have been awarded a number of plates both manufacturer & dealer. In both cases the plates and the respective three or four digit numbers identified either the manufacturer or the dealer with a special number:
“013” for Shelby American as a manufacturer, and
“4101” for Carroll Shelby’s car dealership, High Performance Motors.
The other designations on these special plates were simply sequential for the same manufacturer or dealer: as in 1A, 2A, 3A, or 2H, 2J, and so on. in my research, I have been unable to determine how many of each plate were issued. I suspect those records have been lost through time.
In reviewing some of the photos in the Daytona Cobra Coupes book, I have found that the manufacturer’s plates that were sporadically used on some of Shelby’s cars of that era were largely “013” plates and another one using a similar-style plate that was commonly used by car dealers, with the numbers “4101”. So “manufacturer plates” and “dealer plates” were very similar in design. These plates are traditionally used by manufacturers and/or dealers to move cars around, including public roads, (legally) before they became registered by the owner. Therefore, one plate may be used on any number of cars over time. In the industry, this is known as soft-plating. Shelby also frequently chose to use these on his race cars (as required in, especially, many of the FIA’s European races).
As for Shelby American's manufacturer plates (MFG) and dealer plates (DLR), I’ve seen photos in the Daytona Coupes book (mentioned previously) using both “013” and “4101” plates, respectively. For example, in 1964, at Reims, both “1A 013” and “1E 013" manufacturer plates were used on Daytona racecar numbers 15 & 14 respectively.
At Le Mans in 1964, "1E 013" was used on Daytona racecar number 6 “1E” was used on Daytona racecar number 5 (the eventual winner) and “1C” was used on Daytona racecar number 6. These manufacturer plates were also used on a Cobra roadster at the Freiburg Hillclimb and the Sierre-Montana Hillclimb on Bob Bondurant’s Cobra – for this particular manufacturer plate, “013”, was used with a vertical “1C” and a vertical “MFG” with the “013” manufacturer code.
In the case of the dealer plates, I’ve seen photos in the same book using a vertical “1J” designation and a vertical “DLR” with the 4101 dealer code. These plates were used in 1964 for the Monza and Tour de France races on a Daytona numbered “188”.
So here comes an amusing (and perhaps dubious) anecdote about the “013” Shelby American manufacturer plates. Of course, every car manufacturer wants a plate with low numbers, and as you’d expect they were all taken years before Shelby American was even a gleam in Carroll’s eye. But knowing Shelby, he likely said something like, “Well then, what’s the lowest number you got?” Carroll was then told “013” because nobody wanted ‘unlucky’ 013. Carroll, then said, “Well, I don’t give a damn about unlucky numbers, I’ll take "013!”, and the rest is history.