If there was a standing order to declassify all materials Trump took to Mar-a-Lago...

then markings on the documents seized are irrelevant

So there a ton of rumors and everyone seems to be trying to fit round pegs into square holes on this one. The issues are simple:

• The Presidential Records Act has no criminal statute. There is no manner to charge someone in this dispute. That is why everyone references 18 U.S. Code § 2071 when they talk about criminal charges. Many times trying to make you believe that the penalties from this code are the same as violating the Presidential Records Act. They are not. 
• 18 U.S. Code § 2071 is the removal of classified information. It would not apply if there was a standing declassification order. These documents were moved while he was still President and would qualify under the standing order for declassification. 
• The existence of this standing order is not difficult to ascertain as the President was known to work after hours at Mar-a-Lago and would many times bring classified documents home with him. Nobody from the Trump White House disputes that this standing order existed. So if this is a crime now, it would have been a crime throughout his Presidency.
• The ability of the President to declassify documents has been seen by the courts to be pretty liberal. Examples have existed from President to President of instant declassification. If the FBI tried to charge him with 18 U.S. Code § 2071 - the courts would likely toss that out. However, most of the legal analysts that I read do not believe the DOJ would charge this (especially after not charging Clinton).

This is why the buzz has been about the "espionage act" (18 U.S. Code § 793) rather than the Presidential records act or the concealment act (18 U.S. Code § 2071). The espionage act if focused on military issues (thus the nuclear angle) and requires a much more specific proof of intent. This might explain the larger court order to justify taking just about anything they wanted from the Trump residence. If viewed through this lens, they are attempting to find any evidence that Trump was planning on using this information for the purpose of "harming the United States" or providing "advantage of any foreign nation" which would be necessary to make that case.

Of course, Andrew McCarthy is absolutely convinced that the entire thing is a pretense to garner an all encompassing warrant in order to go after materials tied to the Jan 6th investigation. Under this theory Garland and Wray would have gone to a judge with a "tip" or something suggesting that Trump had dangerous national defense secrets and was just about ready to use them for nefarious means and that they needed a broad warrant in order to stop this conspiracy from happening. All the while, they were just looking for an excuse to look for materials from Jan 6th (for which they would likely never get a warrant for).  

Time will tell who is ultimately right. But unless the FBI uncovers the actual nefarious plot to go along with the documents that they took, then they are going to come out of this looking very poorly to most Americans. Moreover, even if they happened to find something Jan 6th related, the legal debates on the legitimacy of gathering that from a warrant regarding national security would be intense. 

Many of these questions could be answered if the AG would only provide the affidavit for transparency so we would know the actual pretense for this raid. Only then can we judge both the legitimacy of the military style raid as well as judge the relevancy of what it is that they found.