Thats most likely been silkscreened, base don your picture (I could always be wrong), see how you are sanding off multiple layers of solid colours other than black, that called "rich black", you put solid colours of 80-90% blue and/or 16% red underneath the black first and the result is not a boring matt black, but a dark rich colour black. Digital printing would have a fade colour pattern, not solid.
The easiest way to check also is to look at the print with a magnifying glass, silkscreen is screened at around 195-250 lpi, yes Lines Per Inch, no DPI and older digital vinyl is around 140 - 170 lpi, they cant really do more because the nozzels clog up ( the new HP indegio's and other large format vinyl printers have gotten better), how they get around that is the ink bleeds out a little and goes a bit fuzzy, where the silkscreen dots will be tack sharp
In your picture the hot point of the light is also a tell, vinyl would not have that subtle patina.
Now the same old twilight red faded problem, back in the 90's when i was doing large format signage there was a red that was in the market for about 7 years that was called "ferrari red", it got pulled off the market in 1998 because people started realising that it was prone to early fading, in those days you would supply a pantone number they would match to a RAL chart or stock ink chart if they could not get the pantone mix you needed, most of the time the standard stock red as a base to mix from was much cheaper beacduse you could buy it in larger volumes.
Now I cant prove it but the red in the cab is most likely this old prone to fade red that was pretty much the standard go to red in the 90's, but every single Twilight I have seen in the last 5 years has the same fade problem in the sunset graphic, so its kind of interesting.
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