Luxury watches such as the Tag Heuer Formula 1 are subject to knock-off artists --- people who make fake versions of the watch. And while some people may be completely comfortable with a fake version of the original, others want the genuine article and need to know how to spot a fake before making a purchase. While Tag Heuer offers watches that are not very far from the average watch buyer's price limit, price is not the only way to tell a fake from the real thing.
Observe a photo of a genuine Tag Heuer Formula 1 watch and compare it to the suspected knock-off. If the bezel of the watch is not perfectly centred, the watch is a fake.
Place the suspected fake Tag Heuer Formula 1 watch up to a light source for a few moments to "charge" the luminous dial for glowing in the dark and then observe the dial in the dark. If the dial does not glow strongly or does not glow at all, it is a fake. A genuine Tag Heuer Formula 1 watch uses LumiNova, a substance that keeps the watch glowing in the dark strongly over a period of years.
Examine the crown of the suspected fake, paying specific attention to the logo; it should be factory-pressed into the steel if the watch is genuine, as opposed to glued on cheaply. A fake may even have residue of glue and uneven edges on the logo and the crown.
Observe the movement of the watch, giving attention to winding and the movement inside of the crown on the face of the watch. Smooth movement is a signature of a Tag Heuer watch, as opposed to stuttering movement typical of the ticking of a watch.
Hold the watch under direct light and check for dust, debris and/or fingerprints, a sign of sloppy assembly, which is divergent from the stringent quality control of genuine Tag Heuer watches. Using a jeweller's loupe, observe also the printing on the dial of the watch. If there are any messy edges or blurriness in the printing, the watch is a fake.