Dąbrowski has an unidentified “Symbols of the Ancient and Accepted Scottish Rite”, see below. Judging the text in the triangle, it is from France. The lamb appears on the regalia of the 17º degree. It doesn’t appear to be a Paschal Lamb (which has a flag). I don’t know where the image refers to.
In Les Plus Secret Mysteres (1820) a lamb laying on a book with seven seals (like below) and both are displayed on the front of the Ark of the Covenant.
The seven seals which belong to this book, signify the seven Degrees of Masonry; & the lamb laying down on it, which is the Shekhinah, shows us that, He alone is worthy to break the seals, it is only the true Rose Croix who enjoys the privilege of reading in the book that contains the complete doctrine of Masons, & of penetrating the most secret mysteries.
The lamb laying on it, represents the Shekhinah (presence of God).
Voss lists the lamb as the first in the chapter about Symbols of the First Degree and explains it as “innocence”.
In the Fonds Gaborria, we also find a lamb on the second page of the the 47th degree (Chevalier d’Orient”). Ravignat calls it the 61th degree.
The ritual (in Ravignat’s translation) says: “Candidate: wears […] the jewel […] with a lamb on a book of seals […].” Apparently a book of seals is indeed what it is supposed to be.
Top (both): Dąbrowski P. 212. Year and designer unknown.
Bottom: Bibliothèque Numérique Patrimoniale, Fonds Gaborria Ms.-351