Vintage White Castle Hamburger Coffee Mug Blue Logo Mayer China PA 469 For sale is the 1969 White Castle Hamburger coffee mug shown in the listing photos. The mug measures ~ 3 1/4" X 2 3/4", was made by Interpace USA in 1969 and shows extremely modest to no evidence of use or wear. The back stamp changed again in 1969. Here’s the backstory - in 1964 another famous restaurant ware company, Shenango China of New Castle, Pennsylvania, bought the Mayer China company. In 1968, Interpace (International Pipe and Ceramics) bought Shenango China and, by default, Mayer China. So, beginning in 1969, the Mayer China back stamp was changed to reflect the fact that Mayer was a subsidiary of Interpace. This was denoted “by Interpace” under the monogram Mayer China logo and was applied to White Castle mugs from 1969 until they were discontinued sometime in 1978.