It's really good!

Absolutely amazing collection, thank you for sharing!

replacing parts left & right and polishing to like new condition. 

It's the Watch of Theseus!  Begin philisophical debate about if it's actually the same watch...

For me, the only replacement parts should be ones that don't work at all. Broken shaft, messed up mainspring, or a hairspring that's gone haywire?  Sure.  Perfectly good wheels that just aren't as pretty, or a bridge that is tarnished?  Nope, leave them alone.  It adds character.

I'm not sure where the line is; if you use vintage/NOS parts, then you could make the case that it's still a vintage watch.  But if you're using brand new parts?  At some point it stops being "vintage" and starts being "vintage inspired" or maybe a "restomod."

As with those silly display case backs, who looks at the back of a watch?

I have a watch that has both, actually -- an engraved display back.  And you know what?  I love it, and do look at it every time before putting it on.  It brings a smile to my face, doubly so because of the sentimentality of the engraving (my wife had it done for my first ever Father's Day), and the joy of seeing the movement ticking away.

I've used both Tickoprint and Watch Accuracy Meter.  One of my hobbies is electronics, so I had an old piezo element around that I soldered to an old headset lead, and use that with these two apps.  The piezo isn't sensitive to most of the noise you commonly have around the house, but is sensitive to the sound your watch makes.  It works surprisingly well, and they tend to agree with each other, which I guess means they're either both right or both wrong in the same way.

These days I prefer Watch Accuracy Meter, because it gives me the beat error for free.

If you want to go really DIY, check out the microphone and amp info at the Watch-O-Scope site.

You're not wrong, it's crazy bright.  But, at that level, it burns through the battery quick.  Fortunately, it has 3 other brightness modes - 1, 30, and 180 lumens.  I keep mine set to 30, unless I'm looking in the chicken coop at night, then I bump it down to 1 so as not to disturb the ladies.  180 is used sometimes, but 700 I rarely go into except to show friends how bright it really can go.

If you get the right pen, it can be just as lethal as a knife.  Check some of the "tactical" pens out there (some are actually quite elegant), especially the ones with glass breakers built in.  I would not want to get punctured by one of them...