Just a thought, because I don't know where you bought your frothing pitcher from, but I've noticed there are a lot of metal products out there being called "stainless steel" when in fact they are not, and you just don't know for sure until you get them in hand
I've noticed a lot of this on Amazon and eBay because the Chinese sellers use a bunch of tag words in their descriptions, sometimes to point of contradicting themselves ~ like using every known metal in the description, well it can't be all of them
Plus, true stainless isn't cheap ~ no matter the size. I've been trying to change out my metal beads and clasps for jewelry making from sterling to stainless for years, but stainless steel beads are freaking expensive and size variations can be hard to find. When I was looking for a stainless steel bowl for soap making I was thinking to myself I could buy a lot of stainless steel beads and clasps for this amount of money!