I had a similar issue when I found an old iron chair in my grandfather's house. I was really curious if it was vintage or valuable in any sense. I took it to a local shop, but no one could actually identify it. That’s why I decided to check on the internet if there was any information. After hours of searching, I ran into this website https://trimthatweed.com/how-to-identify-vintage-wrought-iron-furniture/ and it really helped me because it had a page about vintage furniture and how to identify it. Because of this website, I was able to identify the chair, and it was actually vintage from 1911.
You need to go to an appraisal company. I strongly advise you to go to a trusted company; otherwise, you may fall for fraudsters. We learned it the hard way.. One of these "companies" was selling appraised furniture of their clients. We bought a vintage dining set there and decided to put it in the garden. But it turned out that it was just rubbish that looked vintage. I was so upset because I wanted a beautiful garden with a dining set, where you could relax in good weather. Later we bought other furniture (if you are interested it’s here: www.gardenfurniture.co.uk), but an unpleasant residue remained.