10” (25 cms) long. 1.5” (37 mms) diameter.

Aluminium rod anode. Concave aluminium cathode.

Thin platinum anti-cathode target deformed by the intense heat generated by the impact of the electron beam.

Looped platinum wire external connections.

Glass discoloration on the anode side of the tube due to long use.

Undated. Unknown make. But the thin square-shaped and the thin bare platinum target make me believe it should be a contemporary of the Jackson focus tube (1896), or  a slightly later type. 

In later tubes the thin platinum target is round in shape and embedded in a metal support.