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The address of the wallet begins with the letter "3" which is the address Mutisig! It is more difficult to guess than the address with "1". Hope someone succeeds!
Good luck!
address starting with 3 used to ONLY be multisignature addresses but after introduction of Segregated Witness in 2017 these addresses that start with 3 can also be SegWit addresses. it is a nested thing with witness program in a script hash thing (P2WSH?) which results in the address to start with 3.
although the creator of the puzzle has not said anything of sorts as far as I know and unless there is a transaction from that key we can never know for sure either.