This article originally appeared on Real Simple
Many millenials likely think of Pyrex as the glass alternative to Tupperware—i.e., sturdy (albeit heavy) containers for leftovers or lunches. But to avid collectors, the heart of the product line is actually the opaque, brightly colored dishes produced in the 1900s—some solid, some patterned, all made from the iconic durable glass. Despite the fact that the brand continues to manufacture new products, vintage Pyrex is highly coveted, and could be worth thousands, according to NPR.
Corning Glass Works launched the Pyrex line of products in 1915, becoming the first company to introduce a kitchen tool made with temperature-resistant glass. Early items included casserole dishes, pie plates, loaf pans, and teapots, and many home cooks have held onto these pieces ever since, according to the Smithsonian. In 1947, the company debuted their colored line of products (previously, the items had been made of clear glass).
Looking to get in on the collecting? In addition to searching your grandma’s house and garage sales, check out the wide variety of items on Etsy.