Hy-gain 5, Modle 674B added board inside radio

[Trapper_267]

Ive picked up 2 of these Hy-gain 5, Modle 674B's with this little board atached to the top of the main board and i was wondering what it was.
There's a piece of foam attached to the top cover to keep it from shorting out.

Anyone have any idea's what it is,  What it does and where i can find any info on them?
Thank's Trapp.

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[Trapper_267]

And i just realized this is the AGC Board that's shown on page 42 of the sam's book CB-129, It's axually called the 2nd stage board or 2nd design
.