We used to ride the rounds of the six nations pre 65 trial, In Gressenich, Germany, as long ago as 1992, they were checking helmets for conformity to EU/FIM regs /ACU spec not sufficient, this was for a closed circuit off road observation trial, all held on private ground with no road work, other than crossing a road from the paddock to the event ( where you had to dismount , kill engine and push across the single carriageway rural road.), needless to say we borrowed a helmet for scrutineering and just wore what we brought with us. We were still riding similar events in the UK with no helmet at all !
In Beauval France where there was roadwork we were able to take the riding number front plate down to "scrutineering" where they stuck a "scrutineering pass" sticker on it !
In the UK, March Hare, Cotswold Cups rounds there was no scrutineering at that time !