William Heinemann reprinted GOLD MINE a few times: in 1974, 1979, 1984, and 1989 for a Uniform Edition.
I once asked Wilbur why the Dedication / Foreword page is missing from nearly every copy of the first Heinemann edition of GOLD MINE. A screenshot of my question and his response from July 2001 are below.
However, I recently acquired a letter from a Roger Smith to Laura Beadle, who worked for Heinemann in June 1990. Roger's explanation to Laura is not the explanation that Wilbur provided to me. See an image of the letter below.
My copy of the Collector's Edition published by Heron Books is pictured below.
A nicely-inscribed copy that is not mine, that I found on the Internet
Doubleday never reprinted its first edition or published any later editions, so all copies are first printings of the first edition.
Many copies of the this edition were remainder-sprayed by Doubleday. It is tough to find a copy in collectible condition that has not been remaindered. I have owned copies with remainder spray on the bottom page edges of the book. Below is an example of what remainder spray looks like on Doubleday copies of GOLD MINE, DIAMOND HUNTERS, and EAGLE IN THE SKY, with THE SUNBIRD in the middle without remainder spray.