That’s a pretty standard mark so these are fine !! I am afraid the values in todays market are going to be less than that amount !! You do not need to find the exact same lamp to establish a value !! Just a similar style and size from the same era !! Blanc de Chine is a white porcelain from China however your lamps were made in USA as you said so that term is a bit misleading !!
Was that appraisal for the pair ?? Or each ??