I thought the
3278 was the most common. If memory serves, the 3274 is a
terminal controller. I think the 3276 is a direct-attached terminal
with a built-in terminal controller.
You are right, memory is vanishing... :o(
The 3278 series always reminded me of mushrooms.
Anyway, they are getting quite scarce, so if you find one, please do
not trash it. Some are modified versions used as consoles for the
mainframe line. The hardest one to get is the squished 3278 - the tube
has a 2:1 aspect ratio, only 12 lines of text yet all the columns, and
was used as a S/3 console.
--
Will