[Chas]

...but I don't have a capacitor tester that measures for leakage at higher voltages.

That is fine on the cap testing with Ohm meter. The Dublier 601's are vacuum impregnated and unless under water or scorched will be fine. Great news on the audio transformers. Modern windings do not use glassine in between the layers the turns are closer together so the added capacitance shunts the higher audio notes.

Recall the MUD parts, re-solder every connection, loosen and re-tighten every electromechanical connection. This is sort of "shotgun" approach, but the mixed metals in both a mechanical and soldered joints do develop a poor connection after some 98 years.

Some of the sheen on the mud parts can be restored by using a modified French Polishing approach using boiled linseed oil rubbed in. Be sure to properly dispose of linseed soaked rags they will spontaneously combust.

Seal the parts (the linseed) to restore the intaglio first, then look to Markal 80220- Paintstik Original B Solid Paint Marker for Oily, Icy, Wet, Dry or Cold Surfaces, Weather- and UV-Resistant, White Color, This product ages in a few weeks to a light wheat color rather than a stark white color. The act of sealing prevents the colorant from creating a whitish haze in the area of application...

GL

Chas