When was the last time a block was solo-mined? Was curious about it the other day, what would be the quickest way to check for the last block payout minus the transaction fee to know when the last block was solo mined?

Thanks.
It is impossible to know whether a block which has no identifying characteristics (i.e. the miner did not put some sort of signature text in the coinbase) was solo mined or pools mined.

The payout values have nothing to do with solo mining.