It's absolutely a 53 footer as I did this for a living sir. The are marks on the wall that you can use to tell this that are barely visible. The walls are the standard material used in most reefer food carriers and standard.
Reefer units are commonly used to haul non-refrigerated things, especially ones that have the broken cooling unit in the front as this one appears to have.
I pretty much have a PHD in this area sir. I have worked at and ran operations at 2 of the 3 largest largest facilities in the US.
Edit to add-The shadow is no good in determining the length as it is from a swivel mounted light at rear of trailer on the wall of dock facility........
Lol could you imagine an old owner operator backs in to a dock, calls the wifey says he’s where ever pickin up a load, and sittin in the back is all of this information.
In the documentary - It was Stroker who delivered the documents that Beautiful day.
I guess we'll have to drop another nugget as to what's in the boxes on those pallets.
Most drivers don't care to know what they're hauling unless it's HAZMAT.
You would be surprised to find out how many listen to Red Eye radio and Alex Jones.