When Ford-Lincoln-Mercury and the postal carrier from California (Clark) are about to be executed, and Ford introduces himself, we flash to a distance shot, in which we see Clark remove his hat. We then flash to a closeup, and Clark removes his hat again.
The main character assumes his role because he found an old abandoned mail truck containing the remains of a long dead mailman and pilfered the uniform from the skeleton. The problem here is the condition of the clothing he takes. When a person dies, the body goes through many stages of decomposition on its way to being merely a skeleton. As the tissues break down, many chemicals and enzymes are released, including the hydrochloric acid of the digestive system. In the final stages of decomposition, this is referred to as liquefacation or liquiescence. Given enough time and a suitable environment this combination of byproducts, with the addition of the bacteria that will inevitably emerge, would make any cloth or fabric (with the exception of treated leather products) not only disgustingly filthy, but also so weakened from exposure to what amounts to a corrosive liquid, that the fibers would tear apart from any stresses put on them. Even the act of taking the jacket off of the remains (and certainly that of putting the jacket on himself) would have pulled the fabric apart.
When the soon-to-be Postman removes the jacket from the skeletal remains of the actual mail carrier, an oil lighter falls from a pocket. With difficulties, it lights...although it shouldn't have lighted at all. These lighters are far from air-tight, and the fluid in it would have long before evaporated.
In a filthy, lawless, post-apocalyptic world where the remaining humans are dressed in rags and barely surviving, Abby still keeps her armpits clean shaven.
The story takes place in 2013, and the Vietnam vet is 63 years old. Tom Petty, apparently playing himself, should also be 63 years old (he was born in 1950), yet certainly does not look that old, especially given the harsh conditions everyone was living under.
In the novel the dead postman is NOT wearing his full uniform and his shirt and jacket are hung over the passenger seat while the dead postal carrier wears a lightwieght Hawaiian shirt. This is why the Postman is able to impersonate a carrier.
As previously stated the decomposing of the mail carrier would have eroded the material of his clothing & leather jacket - but anything remaining would have dry rotted and added to the clothing falling apart.
Prop error:
After the postman is found by the girl, he returns to pine view and is given a place to stay. On the door there's a rusted hubcap - based on the year portrayed in the movie, the era of the hubcap is such that it would've been aluminum alloy and not able to rust. It would maybe have its 'chrome-look 'peeling off, and or show whitish oxidizing, but not rust.
As The Postman and General Bethlehem are starting their parley in the climactic scene, a cameraman and camera are visible on the rock face behind the General.