Note - This password must have been set by whoever used the test rig before me

I guess there is a memory card slotted in CPU. Do you know if this is a RAM or EPROM? In case you don't have a card ot that memory is a RAM using MRES key will delete password. In case of EPROM you need a PG or USB prommer and in Simatic Manager->File->Memeory Card->Delete. Like an option is to use another memery card (EPROM) eventually.

Best regards,

Hristo Mihalev