Factual error: In the scene of Jimmy driving with his new Mercedes, we can see a Subaru forester that is definitely a model after 2010. Season 2 is set in 2002 so this couldn't be possible.
Factual error: Around the beginning of the episode, Saul is entering a Ford F-550 Bus from Sandpiper, but that body style from the Ford F series isn't introduced until 2012+ and Better Call Saul takes place in the early 2000's, 6 years before Saul meets Walter.
Inflatable - S2-E7
Factual error: A Chevy Sonic is behind Jimmy's car, that car was not available until 2012. (00:15:00)
Inflatable - S2-E7
Factual error: In the flashback scene in the store with young Jimmy and his Dad, Jimmy can be seen leaning against a shelf with cans of a "Psst" brand product which did not exist in that time frame.
Factual error: At the start of the scene where Jimmy films a commercial at the school, kids are shown on the playground. Many of them are wearing leggings or skinny jeans. The episode is set in 2002, when the trend was flare and straight legged jeans. The skinny jeans and leggings trend didn't become widespread until 2009 or 2010.
Answer: It might be the Panavision cap he wore when directing his terrible commercials.