The 3C33 is a twin triode power amplifier. The circuit given in the datasheet shows the valve being used as a switch driven hard by a square wave generator.
The RCA Transmitting Tube manual describes the 3C33 as being for industrial control and voltage regulation.
The envelope form is the same as the VHF power valve 829B that dates from the late 1940s.
The twin triode sections seen end on. The Type designation is etched into the glass and is contained within the RCA octagon.
The RCA logo. The anode connections pass through ceramic spacers that fit into the top mica. The fingers on the top mica grip the glass walls.
Looking onto the top of the envelope. Ceramic spacers, flat sided cathode and copper control grid supports.
The B7A base pins look unused and the glass is polished and new. The active area of the anode has a central flange to add extra area and the sides are bounded by flanges that are moulded around the rod supports.
The wide glass tube envelope is 51 mm in diameter, and excluding the B7A base pins is 74 mm tall.
Reference: Datasheet & 4038. Type 3C33 was first introduced in 1946.