I have searched for "odometer correction" and "mileage roll-back" and a few other terms and haven't exactly found the answer to this question.

I am starting to look for a b5 or b6 a4 with less-than 120,000 miles. My understanding is that pre-2004, the odometer reading is easily "corrected" (falsified) with the appropriate tool, even just a VAG-COM or similar though there are numerous devices on ebay seemingly with the express purpose of roll-back.

Is there any way to detect these alterations? For example, if I had the appropriate scanner, could I see the date or number of hours since, (or even just whether) the odometer was reset/ installed? OR, are there other hints, such as # of hours driven * average speed that might betray an ODO alteration?

If not, what about physical tells that the ODO is lying? I imagine it is a lot easier to tell when a 80kmi car is rolled back to 20kmi than it is to tell a 180kmi car from a 90kmi car, as there would be so much variability in the seat wear, etc at that point. For that matter, I guess if I was going to make such a lie, I would replace the driver's seat too.

Of course there is carfax and ideally service records. But say I came across something very tempting with no records and an unilluminating carfax report. What could I do to corroborate the ODO? Does carfax get ODO readings every time the car is inspected or just at registration?