Nearly all appraisals "real and personal property" are subject to USPAP (Uniform Standards for Professional Appraisal Practice) as set out by the Appraisal Standards Board of the Appraisal Foundation. In this case, the appraisal of this collection would fall under Standard Rule 7 which covers development of personal property appraisals and Standard Rule 8 which covers personal property appraisal reporting.
Without going into all the details, I believe that the confidentiality provision applies here. Although, no values were discussed, photos of the collection were displayed/disclosed, hopefully with the client's permission.
Here's a link to the Appraisal Foundation
https://netforum.avectra.com/eWeb/Dy...bCode=HomePage