Absent a CRT tester, about all you can do is check the CRT filament pins for continuity. A few ohms means the filament is intact, infinity means it's a dud. You can find tube data sheets here:
http://tubedata.tigahost.com/tubedata/
It might have an intact filament but still have weak emission, of course.
Phil Nelson
http://antiqueradio.org/index.html