Thoroughbred mare with a tattooed lip?

I just bought a 10 year old white thoroughbred mare from a woman who rescues horses. today i noticed when i was checking out her teeth that she has a number tattooed way up where her lip starts.. and i know there's a way that i can look it up to get information on her but i don't know how. i don't want to get her registration papers (if she has any) because the only thing she is is a loyal friend and my trail riding companion :) i'm just curious on her bloodlines and who owned her, what they did with her, etc. also, because she has a tattoo, does that mean she was a racehorse?