The F6060 is a special quality double triode with flying leads rather than pins as in the 6060. The 6060 is the Brimar equivalent of the Mullard M8162 special quality version of the ECC81 VHF double triode. It is useful for RF stages, oscillators and frequency multipliers, but the construction is slightly different to the ECC81.
The envelope has a large T on it. Eric Calvert who donated the valve points out that the T stands for Trustworthy. Clearly built for long reliable service. Thanks Eric.
An indication of the box anode. This measures approximately 10 mm wide and 9 mm from mica to mica.
Looking into the small anode box the single grid is revealed. The grid wires run flat across the cathode.
The thin glass tube envelope is 20 mm in diameter and excluding the B9A base pins, is 50 mm long.