Holt's work on the Gold Double Daric, now called the Alexander Medallion, has been published as (or rather, in) a book: Frank Holt and Osmund Bopearachchi, "The Alexander Medaillion. Exploring the origins of a unique artefact" (published by the authors, 2011), which brings together several papers on this subject. The authors consider the serious problem of the coin's authenticity, concluding that it is genuinely ancient. But there are many who do not accept the piece, and there is likely to be controversy for a long time to come.

Thanks for posting my request via Anne Bentley of the Massachusetts Historical Society. I recently received e-mail from Frank Holt. He states his papers have just been published in book form, titled "The Alexander Medallion" The book is coauthored by Osmund Bopearachchi, and published in France by Imago Lattara. At present I have not found any book dealers with copies.