Unadressed so it is obviously philatelic but you say that. I have do not understand why people want unaddressed FDCs that have never been through the postal system anyway.
Sure you could also make "commercially used" but the address and corner card would have to be different. I prefer items that go to commercial companies or air mail to a foreign destination for those rates that apply. Nothing is foolproof however. Also I do not collect past 1995 so no modern stuff anyway.
One point though is that I would
not pay high prices for any of these no more that $1 per cover. They are just items of interest. In fact all my
ebay saved searches have "-FDC" in the search terms.
AQ