Got to say - am genuinely delighted that testers are actually looking at the chassis number on the vehicle as I suspect some 'passes' are on vans with numberplate changes, which are then swapped back and sold as MOT'd!
My 74 doesn't have a hard stamped chassis number, just the riveted plate behind the drivers seat. They ask to see it every year. I point to where it is but they can't get to it to see it. The US buses have a plate on the dashboard which is a bit better I think.