I've been saying for years that future archaeologists will wonder at these mysterious emblems they dig up, generally associated with a large deposit of what was once highly refined iron, aluminium and copper. About half a metre wide and 11cm high, made of incredibly durable plastic obviously intended to last for centuries, if not millenia.
And they'll puzzle over the inscriptions, "G809 BGG", "R420 BRL", "RFS 131Y", "SJ12 EXW", "RE51 CUE" - this on some huge chunk of steel, easily three times as big as the rest, and so many others.
What could they mean?