This exhibit is the M8136 and it was designed as a special quality version of the popular ECC82 double triode. The data-sheet gives values for use in pulse mode.
An amplification factor of 17 is quoted.
This exhibit was made in Great Britain on or after 1970 as the stylised logo appears on the glass.
The reverse has the CV4003 Type designation printed on it showing direct equivalence with the commercial version.
Face view of one of the anodes. The copper grid supports can be seen above the top mica.
The thin glass tube envelope is 20 mm in diameter and the length excluding the B9A base pins, is 46 mm.
Reference: Data-sheet. Type M8136 was first introduced in 1956. See also1956 adverts.