From the introduction:
Palace of the Silver Princess is notable as being the D&D module recalled on the same day it was released, then rewritten and re-released some months later. The original version, with the orange cover, was written in 1980 by Jean Wells. When the orange version was recalled (and most copies destroyed), the module was rewritten by Tom Moldvay and released with a green cover. This conversion guide allows DMs to run the original orange-colored module with 5<sup>th</sup> Edition rules and provides a reference sheet for encounters.
An adventure location for 1st–3rd level characters which also includes a sketched out sandbox setting.
The original module is required for the use of this conversion product.
The entry for B3: Palace of the Silver Princess (Orange) has more information about the publication history and other editions of The Palace of the Silver Princess.