The 12AT7 is the American Type designation. In Europe the valve is better known as the ECC81. It was designed for RF use and is of medium impedance.
The 12AT7 also makes an excellent phase splitter in modern audio applications and is regarded as a better valve for new designs rather than the purpose designed high gain 12AX7 that has a small grid drive range.
This exhibit is British Made and features the green Cossor print.
The two small triode sections seen edge on.
The anode is folded and stitched on one side. The control grid is wound on copper supports but as this is a low power device there is no requirement for heat radiating fins on the tops of the grid supports.
The thin glass tube envelope is 20 mm in diameter and excluding B9A base pins the length is 49 mm.
References: Data-sheet & 1040. Type 12AT7 was first introduced in 1947. See also1947 adverts.
