1966 Fender Mustang "Customized" model?

Hey everyone, I have in my temporary possession an all original 1966 Fender Mustang which is on loan from a friend and local bassist. I am in the process of cleaning it up and doing a fret levelling job and setup to get it back in playing shape. I was just curious if anyone here on TB knew anything about the headstock "Customized" decal? I've looked everywhere and can't seem to find another like it, just wondering if it's super rare or something?
The owner bough this bass in 1978 in Sudbury, Ontario, Canada and played it mostly during his teen years. It has been sitting in his basement unused for many years.

And before I get flamed, I did NOT install those strings!...lol I'll be restringing with flats....

I posted originally this over in basses forum but not getting much interest, thought I'd try here....


Anyway, check it out, it's a super cool bass!

 

As per request, here are some more pics of the decals and more!

 

I tries to get the light as "oblique" as possible, trying multiple angles but couldn't see any outline surrounding the decal itself. It is most definitely under the finish though and not applied after.

I've included some shots of the unusual "melted" finish blems as there's an interesting story behind them. The owner was playing a mosquito infested outdoor show many years ago when one of the well meaning audience members decided to spray him mid performance with some kind of bug spray! He said he never thought much of it at the time, finished the show and put the bass back in it's case. Next time he took it out he noticed the damage...in one of the pics you can see the imprint of the case liner in the melted finish!

Also included some shots of the side dots... not sure if these are standard or not for that era but they look like mother of pearl (heavily laquered over).

Whatever the case, it plays and sounds great now, I'm waiting on some Labella 760F Mus flats to come in so I strung it with some old flats I had laying around...two Sadowsky on the bottom and two Labella on the D&G...still sounds great...I really don't want to give it back!

I think it looks perfectly at home in my stable...

 

No I never removed the pickguard or pickups, but you can feel the pole pieces under the plastic covers, either from wear or just the plastic moving with age I guess. They sound wonderfully full, very old Pbass like but a bit smoother midrange.

 

Seems to be a consensus so far re: the decal....must have been put there by the original owner maybe? I'll ask the current owner more about it, might be a story there. I also noticed looking through pics online that the Mustang Bass part of the logo with the "speedy lines" only seems to appear in basses from 1971 or so...which appears to be at odds with the date stamp on the neck heel. Anyone know if this is the case or was this type of decal in use earlier than 1971 and I just haven't been able to find an example?

 

Nevermind....just saw this...Vintage 1966 Fender Mustang Bass Guitar