I am just a hobbyist with an interest in textiles and history, my guesses are often pretty rough and especially by photo. Sometimes I'm wildly off!
Someone would have to look at it in person (like the no batting might be part of the earlier dates you were given). Looks like you have gone over it well and haven't found any hidden dates or anything in the quilting. Even if you have no one easily found in your area as a quilt specialist, contact a good estate sales house/company to see who they would recommend for a full appraisal or a general asking price. Likewise, a local antique store shop owner might be willing to give you a general idea.
I usually just call and talk to people, explain that I was recently given XX item and need to have a general idea of it's retail or insurance value before deciding what to do with it. And then I ask whether there is a charge -- often there is to set an appointment but maybe there specialist will be in the office Thursday noon and could take a quick peek for free. That's what I hope for anyway
Textiles often don't have as much value as we would hope. Provenance (if you know/can document the story) of the object can help. Sometimes it is a matter of getting the right quilt to the right buyer, and that's where brokers and such can come in handy and maybe they can get a higher price.