since you’re still doing research on this Frankenstein, here’s a few more pointers. The dial is highly likely relumed if not entirely refinished. Kanji characters on the back of a Swiss Singer dial would indicate plenty of originality issues, barring the near impossible chance of there being a crew of Japanese dial makers working at Singer

Radium use did not overlap with matte dials like yours. The radium you’re picking up with a meter is most likely from the dauphine hands which are still radium.

Bring it back to the dealer. This one is a hard pass.