JTM50 vs JMP50. Two 1967 vintage Marshall amps with identical specs up against each other.

[Trouserpress]

These are the JTM's preamp valves (all different brands - opposed to the JMP's throughout JJs)
V1 - V2 - PI:

Rect.:

no or barely visible codes on the preamp valves

 

[playloud]

These are the JTM's preamp valves (all different brands - opposed to the JMP's throughout JJs)
V1 - V2 - PI:
View attachment 155352
Rect.:
View attachment 155353
no or barely visible codes on the preamp valves

Nice collection of valves there. The Valvo is the short plate, "45 degree getter" version (see "D" factory code on the back - code above should be "I60"). Brimar appears to have code "D5"=Apr '65. The GZ34 looks like a "7-notch" Mullard.