I don't see how any machine could be powerful enough, hot enough or whatever enough to remove 1/2 inch thick undercoating but somehow not remove inspection markings.
_____________________________________________ Challenger 1, I followed your restoration for a period of time, and I think you did a truely wonderful resto. You have noted several times that you can remove your undercoating with a high pressure wash. I see you have a high quality pressure washer with the ability to get hi temperature spray. I borrowed a friends super high pressure washer (he spray washes tractor and trailers for a living). My California built Challenger must have had extremely thick undercoated as the high pressure washer scarcely removed a damn thing. I had to come back and use can stripper and straight edge blades and plastic scrapers to remove the undercoating.
I have no doubt of your claim, but did you do something to soften the undercoat B4 you used the high pressure washer???????
