antique scientific instrument looks like 20's X-ray tube

It looks like a 1920's X-ray tube. I'm not sure. It's 18 inches long and weighs 2.5 pounds. It is intact and functional but I would caution against exposure if it is an x-ray tube. Regardless it looks very neat and I will bill actual mailing costs. I'm estimating mailing costs and will refund if it's can be mailed for less. Please no overseas buyers. I'm sure customs would go crazy. E-mail any questions.