Great find, these are definitely authentic.
Looks to be signed by Dave, Adrian, Steve (+ "All The Best") and Nicko (+ "Ta!"), no Bruce.
Probably from about 10-15 years ago, impossible to get a nice Dave Murray autograph like that anymore.
I'd say $100-150, maybe more for the right buyer. The album itself is a classic and the autographs look perfect.
These guys have become pretty difficult (and some of their signatures are very sloppy now), but I'm not sure if people have realized that yet. Not too much authentic stuff out there apart from the fan club photos from 10+ years ago.
Yes, Bruce is the most elusive member of the band. Even if you do catch him these days, the signature is likely not going to be pretty.
Sure wouldn't like to be starting from scratch with Iron Maiden collecting at this late stage, especially with Clive Burr already gone.