Goofs

(at around 35 mins) The fortuneteller scene at the party switches between Jacob's left and right hands.

(at around 1h 8 mins) Even through Jacob doesn't finish shaving (he towels-off the remaining shaving cream off his face), he appears to be clean and evenly shaven.

(at around 1h 11 mins) When Jacob and Geary are walking down the stairs, Geary is holding his briefcase with his left hand. After he says "war games in Thailand" and makes a motion with his right hand, the next shot shows that hand now holding the brief case.

(at around 1h 13 mins) When Jacob's kidnapped and the car makes a turn, the shot is flipped - the car's plate is mirrored.

(at around 1 min) In the film's opening sequence there are 2 UH-1 (Huey) helicopters carrying sling loads (cargo nets slung under the belly) to resupply the outpost in Vietnam. But when the helicopters approach the base there aren't any slings under the helicopters.

(at around 10 mins) The subway train Singer gets off of is marked as the "C" train, heading out to Rockaway Park. It never served the Bergen St. Station. However, the original script called for the station to be the Nostrand Ave. Station, which would have been factually correct. Also conspicuously absent from the train is graffiti, common to the subways of that era.

(at around 27 mins) To match the direction of movement, a shot of the Ford LTD racing around a corner has been flipped, but the license plate, which is now in reverse, is visible.

(at around 38 mins) A support wire is clearly visible on one of the demon's wings during the party scene.

(at around 53 mins) One of the occult books Jacob is examining ("A Witch's Bible Volume 1") was not published until 1984, more than a decade after the movie is supposed to have taken place.

(at around 7 mins) At the beginning of the film Jacob is shown carrying an M-16A1 rifle - the forward assist being clearly visible on the right-Hanna side to the front of the trigger. The M-16s used In Vietnam didn't have forward assists so they were prone to jamming. The forward assist was added later to help alleviate the jamming problem.

(at around 46 mins) When Jake puts his son to bed, there is a crew member visible in the mirror behind him when he leans down.

Numerous times, most noticeable in a mirror.

(at around 1h 22 mins) Louis shouts out for "Jacob Stinger" at one point when he is demanding Jacob's release from hospital.