In regards of the missing I’d tag...
Junk pile build.
Warranty return, refused something something, just send us the tag, blah, blah, blah.
Dealer forgot to move the tag over onto new case, or did a poor job.
Removed from service, tag removed before disposal.
Oddly enough, insurance recovery sale, auction. Usually these are just scratched up badly or stamped over.
Sometimes the things fall off, cause it is a Husqvarna and everything else vibrates loose so why not the tag.
Could be stolen, tag removed.
At one time I had a 372 with a tag that was etched with the word DEMO, looked like a dremel tool extravaganza. The case had hash marks dremeled into it. Whatever the hash marks were counting, it happened a lot. Beyond the dremel marks it was in quite good condition aside from needing a crank.
I am not encouraging folks to ignore that fact that a saw might be stolen property, my personal opinion would be that anything with a damaged serial number is likely stolen, however there are other reasons. Best advice, if it causes you concern, walk away. If it does not, it should, ask questions, press for answers, no answers, bad answers, walk away. If the seller will not sign a completed receipt, run away.