I can't tell you if the photo in the following link is authentic but the autographs look very similar to the one you have posted there.

http://cdn103.iofferphoto.com/img/item/809/295/76/o_xFQZV2hsgGVYTGU.jpg

In fact, when I first saw the one in the link, I thought yours might be a pre-print of that one since Tina Louise's is in black on yours and in blue on the other one. But the signatures on a couple of them are placed differently on the photo.

Alan Hale's looks similar in that photo to the one you have listed. I know you were kind of concerned about that. I don't know...they [i]look[/i] very close. Jim Backus loops the "J", doesn't dot the "i" and loops the "B", too. So it could be his signature but with a thicker pen.

While I know nothing baout their actual signatures, it almost looks like the same person signed all these signatures.

Hale's looks almost like there's an extra letter at the end. Was he trying to write "Jr.", maybe? Did he normally add the "Jr" at the end of his signature?

Bob Denver's signature looks like examples I've seen. It's pretty distinctive. Tina Louise's looks very similar to examples I've seen of hers.
It's possible someone could've gotten some of the signatures of cast members who were still living (prior to Denver's death, of course) and added signatures by their own hand for the ones who had died already.

[quote="Wordsworth"]If the signatures were written in a hurry, it could be them. Russell Johnson's signature is cut off at the end of Johnson. On my autograph, which I got from his website (and I presume is authentic), the signature is full. Dawn Wells does loop a Big D for her first name and scrawl the rest of the first name. Her last name is legible, but the "s" at the end of Wells in the photo you show is different from the one I have.

Like I said, if they were in a hurry, they could have scrawled quickly. I can't tell you about Alan Hale. When was the photo allegedly signed? Jim Backus died in 1989, Natalie Shafer in 1991. Just FYI in case the dates are off.[/quote]

Yeah, Russell looks a little different than the one I have of him too. The reason I said Dawn looked a little different is because the oe I have of her, her first name is much more legible than this one.
All of the other Alan Hale autographs I've seen (Don't own one, looking for one though...Same with Backus and Schafer) are cursive. This one is in print.

If the signatures were written in a hurry, it could be them. Russell Johnson's signature is cut off at the end of Johnson. On my autograph, which I got from his website (and I presume is authentic), the signature is full. Dawn Wells does loop a Big D for her first name and scrawl the rest of the first name. Her last name is legible, but the "s" at the end of Wells in the photo you show is different from the one I have.

Like I said, if they were in a hurry, they could have scrawled quickly. I can't tell you about Alan Hale. When was the photo allegedly signed? Jim Backus died in 1989, Natalie Shafer in 1991. Just FYI in case the dates are off.

I'm looking at this photo...

[img]http://i104.photobucket.com/albums/m164/gills53/auto.jpg[/img]

I'm not sure. The one that raises a red flag is Alan Hale and a bit of Dawn Wells...