When cataloging resources that lack explicitly stated info (e.g., statement
of authority, date of publication), my understanding is that one can record
inferred info in square brackets. So in the classic case of CIA maps--which
typically imply through a somewhat opaque alphanumeric code when the maps
were created--the 264$c might look like this:

[2018?]

But in that case, what about the 008 and the 050/090 fields? Is it equally
permissible to put "[2018?]" into those fields? I've seen plenty of CIA
maps, but I'm not sure I've ever seen one with a "?" in the call number!

Thanks.
Michael