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.
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.