You kinda have to go by what you see as most hour meters can be changed or disconnected if someone so desires. For many years Case has used on built into the warning light panel that I'm sure would be expensive to buy a new one to turn it back to 0. If its the older Hobbs meters that many machines used they can be bought anywhere. Even the new machines can be messed with but it takes a new computer ($700) and a dealer that don't mind to do it.
Most used equipment dealers won't guarantee hours or even the year of manufacture. So again its really up to your better judgment.
Ken