Readers of Japanese: what do these words say? (please see inside)

I cannot read the Japanese. It’s too advanced for me. I can tell you what it is, though. It’s a very hard, thick paper square used to write stylized Kanji on and display. It could also be used for painting sumi-e or ink paintings.

Sunshouanshikishi
寸松庵色紙

I think it was the title of a calligraphy book published in the Heian Period

I think that, in a way, you are both correct. You are just referring to 2 different aspects of it. Thank you for your replies.