Vintage 1601 date?

[Archimedes]

Hey everyone I have a Rolex Datejust 1601 with serial number 9900XXX.

I've been doing my research and I can't come to a solid conclusion about what's going on here. I've used the dating tool on Bob's watches and it tells me 1964, but all other sites are pointing towards late 80s. This confuses me because I thought the 1601 was discontinued in the late 70s/early 80s.

If anyone knows what year this is that would be really helpful. And bonus points if you know which movement it uses (if I read correctly 1675 came out in '65 and if this is a 64 watch it would use 1665, though it does have hacking).

Thanks.

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