19 year old broodmare??

Easily. Shay-las mare is 19 years old, and in consideration of her has a broodmare, her state of health wouldn't even be taken into "consideration" - she's foaled multiple times before, and she's a perfect picture of health and vibrant energy. She's only been retired because of an old back injury, but the vet cleared her for breeding and nobody can believe she's 19 years old!

Its not unusual or wrong at all for a 19 year old mare to be bred and not unusual for her to have a healthy foal. Well-managed broodmares can and do keep carrying and delivering foals into their 20s--

Asd an aside, many older broodmares truly love their job. I have personally witnessed mares who were retired from their broodmare careers immediately decline in health and attitude when they were no longer being bred/raising foals. Using a retired broodie as an "auntie"-- a companion and teacher for weanlings and/or yearlings-- sometimes proves to be greatly beneficial for both the auntie and her students.

I think this is the key problem - you do not trust the seller to tell the truth, and probably with good reason.

It doesn't matter if her story MIGHT be plausible, if she is dishonest it doesn't matter if the facts add up or not, it is either the truth or it isn't. I wouldn't worry about the possible age of your horses dam, assume nothing until you have the vet look at her. If she is over the age of around 18 (sounds like she is) you should be able to get an estimation of her age from her teeth. Not 100% accurate however teeth don't lie.

P.S. If you are buying the horse why are you being refused access to her papers?

I worked on a STB breeding farm and a mare there foaled at age 32 but was retired because the foal was stillborn.

Why wouldn't the seller give you the papers? She's YOUR horse now, so you have the right to get the papers.

The papers belong to the person that paid for them. They don't belong to the horse. There are many reasons that a seller may retain the papers but they have every right to do so.

Broodmares are generally bred until they no longer settle or they are unhealthy in some way or they die. What should a person do with a broodmare take her out and shoot her when she turns 20 just because she's twenty?

I agree, you have a right to the papers.

But 19 is fine for a broomare if she passes a breeding soundness exam. My TB mare is 17 and I'm thinking of breeding her again next year, for a 2012 baby... She'd be 19 when she foals if those plans follow through.

I agree with you KevinsHorses that broodmares don't need to be retired simply because they are over the age of 20, however the OP was asking this question in relation to the age of her horses Mother. I.e. Is it possible for the Dam to have been 19 when the OP's horse was born, therefore making her horse 20 (as indicated by the seller).

To the OP: The answer is that yes, it is possible for mares to raise healthy foals at the age of 19, however given your concern regarding the sellers honesty (or lack thereof) I think you should be skeptical of anything she tells you.