I might want to set the valves as many of these old cars have never been touched for eons. Or at least check that some clearances are still present.

Also gives you an opportunity to check the general condition of the timing and components.

I can see someone owning one of these and by pure neglect letting the valve adjustment go undone not even realizing they are not hydralic. Until the point the engine may not even start or only with severe difficulty.

When someone buys a really old car nothing should be just assumed. Another common case for discontinued use could be the glow plug circuit. Or just total neglect of fuel filter changes.

Actually these things should be checked prior to getting into a frustrating experience. The claim of low compression could be simple valve adjustments lacking for almost forever.

As Tom says though it just might just start up. Depends a lot on why usage of the car was discontinued. Diesel engines seem to stand long periods of inactivity far better than gas engines. That's if they were starting and running well until when last shut down.

.Now on those cars that were using vegatable oil and the car has sat unused for a long period because it had developed low compression. The vegetable oil residue in the ring lands will turn into a very strong glue with time. Although nobody as old as the last owner is likely to have used it. So it would be off my radar on this car.