Judging by the nubs, he's prolly correct about the mileage, but that's only half the story. On the sidewall is an oval with 4 numbers in it. The first two are week and the second two are year of manufacture. For instance the one below was made in the 10th week of 2017. You'll want to be leery of tires that are more than about 5yrs old. They'll easily go past that, but if you don't know their history, you'll be rolling the dice.
Heat and UV light are big killers of tires. Tires in a hot climate will be about used up at 5 yrs. Tires kept outside (in the driveway) will be exposed to a lot of UV light... and pretty much done after 4 or 5 yrs.
The tires on my bike are so old, you guys would freak out if I told ya how old....
... but I know their history, when they were mounted and how they were stored, so I have no problem running with 'em. But as I said, if you don't know the age and the history, you're rollin' the dice.
On the other hand, new tires ain't
that expensive, just make sure the selling price reflects their age.
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