No such thing as a COA anymore. Now you have to take the car to the dealer and pay them to "certify" it.

I owned a 1978 930, to me the greatest 930 built because no catalyst and has the intercooler

Plus only 461 made for US market, never care for black market 930. Many reasons for that, later topic.
But as with all Porsche aircooled cars, THEY MUST BE KEPT ORIGINAL TO GET BEST MONEY.

Not saying mds are bad, but mods are a reflection of the owner, I perfer ORIGINAL

The best deal is someone buy your 930 and get it back original, leave paint alone, too much invested to return the color