This mug was in bad condition. It is mix of ceramic and stainless steel. I guess the stainless steel bit was for the purpose of insulation? you know, to keep your hot beverage warm for longer. Rare? we do have stainless steel mugs for decades now and some do mix stainless steel with plastics too. So, innovation wise, not that special but I do think that this mug is the earliest version of stainless steel + plastics+other materials hybrid.