In the waning days of Federal Comics' DC reprint tenure a letter column appeared titled Comic Comments...:
These are useful for dating the issues carrying these letters. Issues containing the first letter can be dated to January 1986, and issues containing the second letter can be dated to February 1986.
That is, if they are printed on the inner covers - the first letter appeared in at least one earlier issue as filler on the last page, and that issue I have dated as December 1985. However, if they appear on the inside front covers - and the inside back cover has a Wham! advertisement - I think you can safely attribute a January or February date to the issue at hand. I've verified this with at least three samples of each.
I think of the first letter as the Dark Maple letter - it does appear to reference the LOC'er T.M. Maple. And in doing so it does beg the question as to whether these were legitimate letters or Federal contrivances. There does appear to be some effort to reference recent local editions... but as I say, my interest in these is in the dating information and guidance they provide, and I really haven't spent much time considering provenance.
Rather, I've been spending too much of my holiday break poring over the Federal DC's and their advertisements with the aim of establishing a dating guide. Lots of stuff to report, and also, of course, a few frustrating anomalies... TBA!
PS: There is a reference to Dark Maple/T.M. Maple on AusReprints, but I don't recall which issue it was related to. I'll update the information when I come across it again. Credit where credit's due and all that...