Stay late at work, get some overtime in & pay an alarm man to set up it....
They should know hoe the different ext modes work
& how to define which buttons does what the keyfob
batteries had failed,
metal backplate + inner cover
2 batteries,
2 pizeos
2 circuits boards
plastic lid....
would have been an expensive item in its day...
A Yale sounder is the only thing which will work on a Yale alarm
It can probably be refinished or repacked to look less "Yale"
However its a DIY alarm, the only time I see them is when they get taken out...