Rick Turner may have confirmed that it was built in 1973.  But the barn shot shows electronics that were not available in 1973.  Just sayin'.

I agree with dela217.
The electronics looks like PF-6 controllers.
Only a few older instruments have same layout, but these are made 72's and have oldest PUs.
 
I think some storys.
If the project started on the finger board inlays at 1973 (It was ordered as 28th instruments.), and the project needs over 12 monthes for finish ? (It was completed as later spec at 1974 or 75.)
I believe original specs (that I uploaded pict.) are just like 74' or 75' (not 73').
 
Or the guitar was frequently updated every year.
But why the serial number on the finger board ?
 
Eiji

One thing I'm guessing is that the guitar was refinished - look how shiny it is on stage. Finish may have filled up or obscured the the original serial number on the end of the peghead.  
 
Barn shots are circa 1973-1976.

If it was refinished, it had to have been done within a couple of years of the guitar's completion judging by the era of the pic. Aside from perhaps a logo switch, I don't see any mods in the Clapton pic to warrant a complete refinish.  
 
Pickguards can hide many mysteries
 
I wonder if they figured how to remove the dummy coil, but also how deep that 2nd pup selector had to be routed in order to drill at an angle from what I'm assuming is the new HB pup route.

Any idea of a date for the pic with Clapton? Any mega-Clapton fans that can date him by his facial hair, etc.? Or Santana for that matter, by his hair, etc. I would guess the Mahavishnu/Devadip phase by his clothes - Love Devotion Surrender came out in 1973...

Saiichi Sugiyama said Clapton played with Santana at 1975 (with his well knownBlacky Strato).
 
I understand the serial number on the finger board.
But I feel the guitar is not familiar with the time line yet.
 
This is my archive's screen shot.
You can feel it what I say.
 
 
Eiji

I see some of my basses in your screenshot. But you are missing two of mine.  You are missing number 16 and number 47.  Unless I am not seeing all of the screen. Great job putting all of that together.  
 
Michael

I see my old  Guild Bass in the upper left hand corner right next to 72-01 !   that's Cool______
 
          Sonic Regards ______

Michael,
Ofcourse I know your No.16 and 47, and there are far left out of the screen.
This shot is triming for Santana Gtr on center.
 
Eiji

This archives are thumbnail basis for quick reference by body type and grains.
It's my pleasure to filling this checkerboard.
 
Eiji

Two questions Eiji:
 
What's the bass below Wolf's Starfire?  
 
Do you have more pics of #13?

Hi Pace,
Please look serial number / history request.
I uploaded whole shot of the bass on One of the first? 72-13 thread.
Of course, there are all pics of 72-13 that I know.
Thanwarin (owner of 72-13) reported the info.
 
Eiji

Sorry for the hijack.