NOTE: Brad Gougeon 2022 - An 1897 Pitkin & Brooks wholesaler catalog shows six varieties of plates offered in opal and jet (black). Listed as No 103 which may be the OMN but not 100%. Of the six plates, one can be documented to Canton - the Trefoil, and two can be attributed to Canton, the Lattice and the Marion (Gem). The other three are possibly Canton but there is not enough evidence at this time to move them to "attributed".
NOTE: Bob Buford 2022 - E. McCamly Belknap in his 1949 book "Milk Glass" shows an 8" square white one, calling it 'Backward C'. "...is one of the choicest of the open-edge plates. It is found in white, blue, and black, and in 7", 8", 8-1/2", and 10"."