When Jim Does his Jimmy Joe Meeker routine with Sofia, he says he is from Houston. He goes on to say that he does not want Mrs. Meeker wearing the same thing that other West Texas women wear. BUT Houston is in East Texas, NOT West Texas.
When Sophia is on the phone in the boutique, the base (a Western Electric 1A2 model) shows no outside line button light revealing it's a fake call. Please note this is very common in movie/television production.
When Rockford first meets Mr. Masters in the mansion and they are standing at the base of the stairs, a boom mic is visible sweeping across the paneling when Mr. Masters turns to walk further down the stairs.