Dąbrowski has an unidentified “Masonic Symbols”, see below. I don’t know in which degree this image is featured and if there are other systems or degrees with this symbol, but I did encounter it on Mark Master tracing boards, sometimes with nine dots. Perhaps it is just a (Mason’s) mark?
The # (hashtag) can often be found together with a X on Master Mason drawing boards. Thus combined (#X) it can either refer to the pigpen cipher or a way to construct cubic stones.
On Mark tracing boards there are frequently two ‘versions’:
Which seems to support the idea that it is ‘just’ a reference to the pigpen cipher.
Dąbrowski p. 166 “Masonic Symbols”, it is the same design as the apron that Lafayette presented to Washington in 1870
There is a specific hashtag system with dots. Find out what is it about and good luck.
I came across Mark charts with the # and nine dots. I haven’t found an (obvious) reference to it in Mark rituals, but I’m not a Mark Master, so I probably miss the context (for the same reason, I don’t want to dig too deep). Or, the symbol is specific to -for example- American Mark rituals.