Dąbrowski has an unidentified “Masonic Symbols”, see below. I don’t suppose this is to be a UFO, so perhaps a hat with ribbon like the symbol of a Bishop? I don’t know in which degree this image is featured and if there are other systems or degrees with this symbol.
Could it be related to the equally mysterious image on this Kloss image (Irish Master degree)?
In the Baylot collection there is a degree called “Maitre Irlandais” which describes a tracing board that is not available in the document, but several elements can be seen above. The XC, IHS, the key, the scales, the urn, but not the most eye-catching thing there on top? Mention is made of a little casket, which could be the thing below the hat/bell, even though in this ritual the casket is in the middle of a tessellated border. Then there is a question about a bag on the apron. Could either be what this is? A bag or an apron?
Top: Dąbrowski p. 166 “Masonic Symbols”, it is the same design as the apron that Lafayette presented to Washington in 1870
Bottom: collection (1844) of Georg Kloss (1787-1854) (Elu des Neuf. – Elu des Quinze. – Maître Irlandais. – Chevalier Prussien, grade Anglais. – Chevalier d’Orient. Avec 45 tableaux Kl.MS:XXXVI.5)