Help with a frequently appearing FBI memo acronym

Hi, folks.

I am looking at some FBI docs from the early 1980s and keep seeing this, “C and E [sometimes C&E] by 1357 [or some other person’s ID no.], Reason 1, DRD, July 18, 2000 [or some other later date].”

My guess would be that this stands for something like “Classified and Exempt by [so-and-so’s internal ID no.], for Reason 1 [whatever that is], the declassification review deadline is July 18, 2000 [or whatever the date happens to be].”

Thoughts/Ideas/Actual Information welcome. For example: What is “reason 1”?!?!?!? [Google searches and site:.gov Google searches have not been helpful so far.]

Thanks. :D