Hello TiN,
It is really aggravating when someone abuses precision equipment like this, I hope they got fired for it, no excuse. You could have a case for a refund given the condition it is in, definitely not in working condition by any definition. That decade was severely overloaded, the resistors are definitely ruined, the switch might be recoverable hard to tell from the photo. The blackening on the panel indicates severe stupidity. If the switch could be recovered, it would be possible to rebuild the resistor chain since it is of Manganin alloy. However, given the design of the 925D, the 0.1? decade has to calibrated to the 925D's 'zero' ohm value which is different for every unit, just 'plugging in' another decade will result in higher error.