This is the first time I've seen a guard with that particular shape--it's got to be an early one. The earliest were minted in 1958, if not mistaken. AMF records are lacking.
Take a look at the AMF logo style--it's ancient. By the early '60's, it already appeared like this:
Before the decade was out, they'd switched to this:
Is the seatpost affixed using an internal wedge (much like a handlebar stem), rather than a clamp? That is also a hallmark of a very early AMF bike.
Yours looks like this one that @Euphman06 picked up a couple of years ago.
http://ratrodbikes.com/forum/index.php?threads/amf-skyrider.57416/
Here are some more of them. Your chainguard does seem to have older styling than the other ones, but none of these have the star ring.
http://ratrodbikes.com/forum/index.php?threads/need-help-with-this-skyrider.57763/
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