quote.............."Do you mean have I looked for a reg mark actually on the bowl?". I do indeed....... on clear glass especially, they can sometimes be difficult to see - it's aguably even quicker and more reliable to run a finger around the inside to feel for the raised digits, than spend time peering into reflections or looking in poor lighting conditions.
I can see what appear to be scratches on the smooth part of the foot, but I'm not getting an impression of great age - sorry.