The CV4003 type valve is a special quality version of the ECC82 double triode itself CV491. Also on the envelope is the Type 6189 and on the reverse the later Mullard logo and the Type designation M8136.
The mechanical design is specifically to enable the valve to withstand shock and vibration as would be found in military and airborne equipment.
This double triode was often used in instrumentation applications as well as audio.
An amplification factor of 17 is quoted.
The maker's logo and name together with Made in Great Britain.
The twin sections without central screen.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 48 mm tall.
Reference: Datasheet. Type CV4003 was first introduced in 1956.