I think yYou're right, a plaque wouldn't really fit for the Brouwer carving.
I think the best way to avoid confusion is by having it clearly flagged up with those who record these things (hence posting it here as a part of that). A couple of times in the past decade, I've had to accompany the CA and a fella who'd found some CnR like motifs in North Tyneside, and even after the CA told them these were accounted for as modern, they didn't believe it until taken and shown how it'd been done.