The patent dates on the slide plate will help give you a ballpark figure on age. It doesn't look like the White made machines I'm familiar with. I'm not used to seeing a front inspection plate on Whites. The stripped screwhole is an easy fix. Glue a plug into the hole, redrill it and re-install the screw.
Amazing what people will throw out.
I think that machine will clean up very nicely. Read the sticky on cleaning these old machines and watch Muv's videos.
I wouldn't use anything more harsh than sewing machine oil on yours. the decals are already damaged. You don't want to make them worse.
Replacement belts are easily available new for less than $10.
Rodney