Pre-cooked foods are now sold in PET trays suitable for reheating in conventional or microwave ovens is this also normal PET?

The PET grades used for 'ovenable' trays have the same basic chemical formula as ordinary PET but it has been specially heat treated during the container manufacturing process to turn it opaque milky white. In this form it has a much higher temperature resistance and is can be heated up to 220 degrees centigrade which is high enough for reheating pre-cooked foods.