OH...Its Porcelain..
Every other part of them seems to be overbuilt,All companies have had troubles from time to time,1954 Frigidaire ovens used snap on side rack guides,that would have been fine,but they also made the oven liner completely smooth,so when it heated and cooled...it warped...when it warped, the enamel popped off,The Norges faults are ,I think, the ridges bent into the liner are too sharp,all the expansion and contraction is concentrated at that point,and I agree,although the outside has beautiful heavy porcelain, the oven liners are not coated thick enough,now in a GE or Frigidaire,its easy to remove the lining,but in these...IT AINT, the whole front frame has to be removed to get the liner out!!!! BUT IM STILL GOING tO GET ALL THE NORGES I CAN FIND!!!!!!!WHY cause I like em!!!!