Ok, a Blu-ray Disc “guaranteed to preserve data safely for over 200 years” is a claim that may not exactly be impossible to prove, but would you (or your descendants) even bother?
Delkin Devices, manufacturer of the Archival Gold BD Recordable media, says that its patented “phase-change” recording materials allow the discs to withstand the effects of UV light, heat and humidity. The company also claims that the 4x write-speed discs have a scratch-proof coating that offers 50 times better protection than the ordinary coating found on other optical discs.
Now, disregarding the question of how Delkin came to the conclusion that the discs will retain data for two centuries without adequate real-life testing, its so-called 200 Year Disc has two potential snags.
Firstly, by 2208, BD drives to read the disc will definitely not be available (barring an unlikely stagnation in technological innovation). Secondly, the data written to the disc is likely to be in a format that is no longer supported by then.
So for all that it’s worth, the 200-year “guarantee” is probably just a cheap marketing ploy.