[Mondial]

Ron, does the TA-600 have the selenium rectifier bias and DC filament supply like the later models? 

If it were mine, I would leave the mylars alone. As you said, they are some other manufacturer's version of the Sprague Orange Drop.

 Pretty much all the US cap manufacturers of the time bought their Mylar film from the same supplier ( Dupont),
so quality should be comparable to Sprague. I have tested several brands of the early dipped Mylar caps and they all test the same, with very low leakage. I have a bunch of NOS dipped Mylars of the same type and have been using them as replacements for years without a single problem