Um, the art world has reported enough forgeries, with period canvases being re-worked. Sometimes, they were a genuine me-too 'In The Style Of' that was later 'talked up'. Sometimes, they have taken a leap in tech to resolve. Beyond multi-spectral imaging, there's x-ray emission spectroscopy which can look at the precise elemental content of ink or paint, report, 'anachronistic'...
I suppose the classic example is the Turin Shroud. Provenance suggests a medieval or renaissance date. Actual age is uncertain because it has been damaged, repaired, damaged and repaired often enough to 'muddy the waters'. Identifying any truly representative part that's 'disposable' to allow robust carbon dating is a sensitive subject...
Worst case, it was an authentic, but plain burial shroud looted from some desert tomb, then accessorised...
There was a thriving market in relic-manufacture: 'Tis said the Crusaders and centuries of pilgrims collected enough fragments of the Cross as wood and nails to build the impossibly vast Noachian Ark. Current equivalent is 'Chinese Fossils'...
I've heard of genuinely old documents being re-worked as palimpsests. Also, IIRC, the Mormons / LDS are still reeling from the scandal of learning their top researcher forged much archival material to supplement his many genuine finds. He had such access, and his extensive output was so perfect, that *everything* he handled must now be considered suspect...