New Tolkien Letter discovered

[Child of the 7th Age]

I am a haunter of e-bay. One of the things that constantly surprises me is how often "new" Tolkien letters turn up there. They are generally advertised by what looks like reputable dealers in rare books. Pictures are usually given of the letters and often you can read/print out the text (which I often do).

Most of the letters are brief replies, but once or twice I have seen something where the professor actually commented on something. I can remember one where he discussed that he had become "tired" of hobbits and didn't intend to write anything more of that type.

How can you tell if these missives are real? I suppose you would have to inquire into their provenance and know something about authenticating signatures. Since all of these letters go for a great deal more than I could afford, I have never inquired further. Yet it does make me wonder: if these examples turn up regularly on e-bay, how much more is in private hands that we know nothing about -- people's attics as well as dealers' inventory.