Hi,new recruit here,just bought a 1980 F-412 in beautiful condition.There`s a pickup attached to the underside of the top,below/behind the bridge.Hard to get a good view,it`s a thick disc,blue in color,doesn`t sound that great,lol.Would this have been factory installed?Also,I found an exact duplicate of the oval paper serial tag that`s in the guitar,in the storage box in the case,model and serial #`s the same on both.I haven`t been able to find any evidence of any repairs anywhere on the guitar,so this seems odd.Thanks for any info.