Possibility of estimating the age of a cow?

[Lucky]

I've got an old black cow that I bought 14 yrs ago as a bred 5 yr old. If this guy said she was 5 she could have been 7 or 8, who knows. She's almost a solid gray color now and still looks good and raises a calf. Definitely the exeption to the rule. Just think 14 yrs ago she was someones cull cow too.