The 6C6 design is very close to the 6J7G with the exception of the inter electrode capacitances. The 6C6 is a general purpose amplifier valve but the close similarities with the 6J7 indicate a good linear characteristic and good suitability for early stage audio amplification.
The Raytheon name and the Type designation is moulded into the Bakelite base cap.
The internal coating and top screen hide the internal details.
The top cap connects to the control grid and the three wire grids indicate a true pentode design.
The classic envelope is 38 mm in diameter, and excluding the UX6 base pins is 107 mm tall.
References: Data-sheet, 1040 & 1043. Type 6C6 was first introduced in 1936.