I just bought this one in Vietnam yesterday.
All parts is shown in the photo, but the mount and tripod have been sold to someone else, I have just only the tube
It has a diameter 70mm and a focal length around 400-500mm, there is only objective lens without eyepiece and focuser or maybe they have been lost.
The strange thing is near the end of this tube has an opaque white plastic plate, only bright light can see through. I used the sun to test as shown in the photo
I think this is a military equipment and maybe It was used in the Vietnam War. Have you seen this device yet?