Good afternoon, Molly,
Thank you for submitting photographs to Mearto for appraisal.
Based on the photographs and information provided, your Bertoia diamond chair is worth $200-300. While these frequently come on the market at auction, many do not feature their original upholstery, which it appears as though yours has. These are still being made so it is difficult to date these but it was designed in 1952.
I hope the above information has been useful to you. Please let us know if you have additional questions, and thank you for using Mearto.