What does “Fireproof” mean on Royal Worcester ovenware?

The “Fireproof” mark on Royal Worcester signifies a hard porcelain designed to withstand sudden changes in temperature and resist thermal shock. The Royal Worcester Museum describes fireproof baking porcelain in 1931 in connection with egg beaters, and the 20th century history page notes that this hard porcelain has been used for “Fireproof” kitchenware since the 1930s. For buyers, this mark helps to place the product in the functional tradition of the oven and table, rather than a purely decorative cabinet product. Even with the “Fireproof” mark, be careful with antiques, avoid sudden changes in temperature, and check for old cracks that heat could exacerbate. Look for clear lettering on the base, consistent factory markings, and shapes specific to ovens (ramekins, casseroles, covered dishes, beaters).