i unfortunately don't know the exact age of mine (it's one that wandered around our area, got to like us because we had food, then later became an actual pet and whatnot) but i estimate somewhere around Mature or Senior
A vet can usually give you a close idea of age by dental examination. They always look at their teeth so if it has been to a vet they may have just not mentioned it but they would know and you could call and ask them. If it's been recent then that would be how to find out or maybe there's something on the web on how to tell by your cat's teeth what their age is.
