That doesn't look like a factory stamped serial number. If you blanked out the last two digits, the number is clearly 5,800,4XX. That's about 5 million numbers too high for a 10-5 and it's missing the prefix ("C" or "D"). I've never seen an overstamp on a serial number either and yours clearly shows one. I think it's been remarked.

__________________
"I also cook."