These Casascius coins were a primitive type of hardware wallet that predate the likes of Trezor and Ledger that are now in common use. I'm not too sure what failed crypto currency system you're referring to here, but Bitcoin, now in its 14th year, is far from a failure in my opinion.
The coins themselves contain access to a private wallet containing the amount of Bitcoin indicated. They have a built-in tamper-proofing mechanism to indicate whether the Bitcoin held on them has been redeemed or not. In this case, all 250 of these are unredeemed, meaning each coin contains its indicated value in Bitcoin, and I guess the grading company adds an extra layer of authenticity on top.
Each of these are for either 1 Bitcoin or 0.5 Bitcoin, so it's expected that they'll sell around the Bitcoin rate (~£22,893 for 1 and ~£11,446 for 0.5). I imagine the majority of buyers will crack these out to redeem them.
Whilst these are mostly now a novelty, they did once have a very practical purpose at a time when little regulation was in place to protect such assets - keeping your Bitcoin on these meant you had full control and weren't putting all your trust in an online wallet destined to fail.