The 6SA7GT is an American design of mixer known as a pentagrid converter or generically as a heptode. It wa used as a self oscillating frequency changer for broadcast receivers.
The Philips brand name of Miniwatt.
The inside of the glass is coated to form a shielding screen and consequently the electrodes cannot be seen.
The wide glass tube envelope is 29 mm in diameter, and excluding the IO base pins is 65 mm tall.
References: Data-sheet & 1043. Type 6SA7GT was first introduced in 1940. See also1940 adverts.
