Inside a Coach bag is a leather patch — the creed — carrying a paragraph about the leather and, on most eras, a serial. On vintage American production the serial is a style number preceded by a factory-and-date code, and the creed text itself is stamped into the leather rather than printed.
Vintage creeds are stamped unevenly by nature: the letters vary slightly in depth because the leather is thick and hand-fed. A perfectly uniform, laser-crisp creed on a bag presented as 1980s production is wrong, which is the opposite of the usual rule and catches people out.
Outlet production carries different markings from boutique production, including style numbers with an F prefix on many pieces. That is genuine Coach — made for the outlet channel — and is not a counterfeit indicator, though it does mean the bag was never sold at the boutique price the seller may be quoting.
Some genuine bags, particularly small accessories and certain eras, carry no creed at all. Absence alone decides nothing.