The 6064 (special quality) version of 6AM6/8D3 (commercial) also carries the Type designations of the service code CV138. CV138 referred to the commercial type 6AM6 first, clearly the 6064 more than meets the original specification. The 6064 usually is deemed equivalent to the CV4014 but the direct equal to the CV4014 is the M8083 and these are specially designed to withstand vibration.
The 6064 is a high gain, high impedance, variable mu, screened pentode. It could be used from AF to VHF up to about 200 MHz and was found in large numbers in most types of electronic equipment. In RADAR, radio & TV it was used for RF and IF amplification. It was also used for oscillators and frequency multipliers.
1040 gives the 6064 equivalent to CV3539 but this is not correct it should be the CV4014 as per radiomuseum.org
The envelope is silvered to prevent electron bombardment of the glass releasing gas the construction differs from the earlier EF91 etc.
Note the shielding.
The top mica etc.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 45 mm tall.
References: Data-sheet, 3002 & 1040 Type 6064 was first introduced in 1951.