Wow! that is a real head scratcher... The tube in the picture appears to be constructed in the same fashion as the 15GP22 (see avatar above), with the phosphor deposited on a flat plate placed behind a decorative mask behind the faceplate. In the "205" (19VP22) tube, the phosphor was deposited directly on the curved faceplate rear surface. The decorative mask inside the 19" tube pictured above must have consumed about 35 sq. inches of the total viewing area. Was this perhaps an early prototype 19" tube made before the process to deposit the phosphor dots on a curved surface was developed?
Picture of "205" CRT does not show an internal mask.... Picture1
jr