Sorry JJ I should also apologise for another double entendre there.
If it's ceramic and doesn't have any cracks or split lines I can't see why it wouldn't be safe in the oven to use (if it does have any splits it could shatter). Ceramic can take up to 260 Degrees C.
no marking on the bottom - it was just the right size for what I wanted to do but i did buy pyrex dish yesterday - a little smaller in depth but I will make it do. Ta