The 0LW26 is a directly heated triode on a B4 base.
The anode in face view.
The filament appears to be M shaped and the valve has mica supports top and bottom.
The top mica has one filament spring above it. There is not a loose spring inside the envelope as the three filament supports above the pinch would suggest. The filament is open circuit and so the other spring must be inside somewhere.
The wide glass tube envelope is 28 mm in diameter, and excluding the B4 base pins is 71 mm tall.
Updated June 23, 2013.