Help me date my 70's J

Just bought an early 70's Jazz from a local music store at a GREAT price.

Music store tells me it's a 73 Jazz. But, they really don't have any proof or history on the bass. The back pickup was dead so they threw it away (died a little bit inside when they said that) and replaced it with some super weird sideways coiled see thru pickup. Sounds cool, just not original.

I get it home and tear it apart to start investigating to figure out the date.

Neck plate has the serial number "305251"
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I pulled the neck off and the first thing I noticed is the giant green "SPECIAL" stamp on it. Any idea what that means? Never seen it before and can't find any other examples of it.
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The date stamp at the butt of the neck is almost completely worn off. The only number you can make out are the first two. Which, to me, looks like a 7 and either a 0 or O. Any ideas on that?
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Here's the rest of the neck
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On to the body. Neck heel was inspected by CHAMBERS and TORRES. Has a "NATURAL" stamp on it.
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Now, I was looking to learn the most information through the pots. I pull the electronics plate and what do I find? Freaking gigantic 750k pots. I'm pretty sure they are not original, but please correct me if I'm wrong.
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Lastly, I pulled the neck pickup and it is 100% original.

So the only solid evidence I have is the neckplate. I read that they started the 300,000's in 1970. If it goes sequentially, it has to be fairly early then, right? 5,200 units after the 300,000's began? I have no idea how many instruments they were selling per year.

Anyways. I'm most curious about the special neck. Any ideas about that?