Need help identifying hexagonal sterling bread and butter plates

Hi. I am brand new to this forum. I need help identifying a set of 5 hexagonal bread and butter plates that belonged to my mother. They are monogrammed with her initial and marked “STERLING 101” on the back. They are American and almost certainly from the mid-1950s. Each plate weighs about 120-130 g (depending on the mood of my temperamental postal scale), but mysteriously, all 5 of them weigh 724 g (maybe because there’s strength in numbers). The only photo I’ve found online that looks like these plates is from a 2014 auction website listing that says: “hexagonal sterling silver bread and butter plates by Sterling Silver Manufacturing Co. of Providence, Rhode Island, marked SSMC / Sterling / 0565; with G monogram; dia. 5.5 in., silver wt. 25.408ozt (790.28g).” But my plates don’t say the same thing on the back, and they are 7 in. at the widest point. Thanks for any insight.