In alchemy this entry sign was sometimes used to signify
oil or wax. In early chemistry it denoted
crystalline copper acetate.
Swedish hobos used it to mean here they give no money but one may get food.
In musical notation it signifies the end of a passage to be repeated, a repeat sign.
In mining contexts it has been used to indicate an abandoned mine shaft, with the circle signifying the entrance hole and the cross over it signifying not valid, or abolished.
In cargo handling the sign sometimes signifies the center of gravity of packages, boxes or cases. Compare with the synonymous . In the USA this sign could mean fine hydrant and groundwater monitoring well.