It's been my observation that the bridge of a vintage Gibson oval hole has to be well south of the pickguard to intonate correctly, and inevitably there is an indentation of where the bridge used to rest.

I first encountered this in the 90s, with a band members mid teens F4. The type where the pickguard has a pin that goes into the hole in the bridge. To intonate even close to being in tune at the octave, the bridge had to be so far south of the pickguard that the pin cleared the hole completely.

I see the same with my own F4, and many others listed. Exhibit A - bridge well clear of the pickguard, marks on top from original position:

Click image for larger version. 

Name:	klp2wdydkakppci589df.jpg 
Views:	26 
Size:	51.6 KB 
ID:	194641

Exhibit B - bridge is flipped so that it doesn't have to be so far south of the guard:

Click image for larger version. 

Name:	ura7yvje9unozcxiotku.jpg 
Views:	25 
Size:	76.5 KB 
ID:	194642

Curious to know why the bridges were originally placed wrong by today's standards - guessing different string tension or something?

With a bridge in original position, hard against the guard, these instruments play completely out of tune with modern strings.