Dąbrowski has an unidentified “Symbols of American Freemasonry”, see below. I don’t know in which degree this image is featured and if there are other systems or degrees with this symbol.
It is perhaps interesting to note that here we see a combination of an ear, a heart and the bell. There is a suggestion that ear, heart, mouth refer to the three principle officers. Could we have a variation to that here?
Feddersen also has Swedish 3rd degree tracing boards with a bell.
Dąbrowski p. 160 “Symbols of American Freemasonry”