In his fourth lecture on R. Chaim Ozer Grodzinksi for Torah in Motion, history professor Marc B. Shapiro says: Now Kellogs has a K, under the Vaad of Boston.
“Often you will have people tell you that when you find a “K” on hashgacha (kosher symbol) on a product, you can’t rely on it because it could just be just packaging. It’s not a trademarked symbol. The company could just put it on. Obviously you should find out who puts the “K” on. Call the company and they’ll tell you. In all the years, I’ve never found a product with a “K” on it without a rabbi behind it.”
