I've never seen an all original one of these, and agree, that's because they are all sold with AM dial, hands and insert. The Water Resist looks sus on this particular dial. Not sure if the date/day window is supposed to be bevelled on these either. Sorry to of been little help .
If it has a beveled D/D.... window and the (SUWA) is a very small one then it is original I would say.
A/M Dials have big SUWA markings, no bevel windows.
Also the Dial Hour markings look very fuzzy/ Hazzy.... when see with a LUME