FWIW... the IGM Approval number is a registered Import General Manifest number not required in the US in the day. Before the EU, all the countries of Europe had their own importation rules and rigid borders and if you wanted to cut through all the rules of 20 or so countries in one fell swoop you could put on file an IGM that met
all their rules and attach it to the item .. like a UL label.. Ergo, the tags with IGM numbers were European destination cars .
Difference Between an Import General Manifest (IGM) and a Bill of Entry I don't know when this was adopted.. It sort of explains why most Spiders didn't have them because an overwhelming majority came across the pond. The Germans and Frenchhad separate rules and tags to define road worthiness in accordance with lighting and safety.