Timing belt

If ever you're unsure, just do it. And the water pump. And the tensioners. With decent quality bits.

the fella who did the belt on my Renault, and he wasn't a main dealer, put a sticker that he presumably found in the bag on the engine, with the date marked on it. If you can't find anything like that, I would change it, as Adrian says.

If a private owner then a reply paid query to the previous owner is always worth a try.

That may simply confirm that the previous owner paid somebody to do it. It doesn't prove anything as to whether the job was actually done!