Great example of a real 5751WA military valve.
This is the longer plate version of the W JAN type 5751s. These are the real deal, ruggedized suited for vibration, high G shock loads, and varying filament voltages found in mobile equipment. These will dial back the gain in unruly amps, and are not merely weak versions of a 12AX7, like current production tubes. They cost more, but they usually last long enough to pay for themselves. Until you try a NOS 5751, don't judge. These are a nice standard to judge from, and make a nice baseline for comparison, as well as a great tube for any amp.