that's the difference,
as toy in a collection it don't matter if it f***ks up & crashes
as working alarm, either I or the subscriber is going to pay for somebody to come on site & get it going should it f**k up & crash
the commercial reality is new controls & an couiple of hours to fit them & hand over is much better value
Assuming they have purchased the property, all the books & service info should have been requested by their solicitor
Its an alarm from the 1980's , it predates PDF, the internet, the mobile phone ect...
Buy a new system
I was once given a big box of books to take to the tip.
I signed loads of 'em & dropped of charity shops
Cliff Richard, Stevie Fry, Jilly Cooper, ect... All use the same sort of marker pen