The symbol used to be fairly current in “craft” degrees, but later started to mostly appear only in adoption rituals or in additional degrees such as Ark Mariners (it is also the emblem of the Provincial there). Especially when combined with a rainbow, the change is big that you are looking at (Royal) Ark Mariner symbolism. The Ark also seems to still be part of York Rite symbolism.
The Anchor And Ark
Are emblems of a well-grounded hope and a well-spent life. They are emblematical of that divine Ark which safely wafts us over this tempestuous sea of troubles, and that Anchor which shall safely moor us in a peaceful harbor, where the wicked cease from troubling, and the weary shall find rest.
Ahiman Rezon. Rituals of Freemasonry by Daniel Sickels (1870)
The meaning is often a reference to the story of Noah‘s ark, but in some Memphis-Misraim texts it explicitly says that the ark is the soul tossed about on the waters of vice.
Interestingly, the image can also be found on an image (of a tracing board) of the oldest known ‘high degree’ ritual from 1747. See here. Also it is displayed on a 22nd degree AASR tracing board from France that I have.
Duncan’s Masonic Ritual and Monitor (1866) by Malcolm C. Duncan