This exhibit is a Mullard British made 12AU7 that is branded IEC - the American reseller.
The 12AU7 is a low μ double triode with a quoted gain of 17.
The 12AU7 near the top of the glass. Inside is the face of one anode.
The pair of triodes seen end on.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 48 mm tall.
References: Datasheet & 1040. Type 12AU7 was first introduced in 1951.