The interior of the trailer is filled with objects that would fly around during transit, including pictures on the wall, books on the shelf, and potted plants. The table is even a folding table, while most trailers have built-in tables. Most people who use trailers would not have so many loose objects. Also, there is too much headroom in the trailer; the trailer is not as big on the outside.
(at around 1 min) Joe has a phone conversation with his secretary, Peggy. The phone booth that each are using is the same one as evidenced by one diagonal and two horizontal scratches or blemishes on the cross bar of the booth. Although shot from slightly different angles, it's the same portable prop phone booth.
When Mannix used the pay phone to call the trailer park manager the close up of the phone dial shows the number (311) 555-2368. This same number was on other phones in prior weeks including an office phone at Intertect.
When Mannix is discussing the case with Peggy while looking through mail, in his office, the open, unused envelopes are all upside down.
Toward the end of the show, Mannix is talking to Peggy on the phone but he calls her "Maggie", a different character in this episode.