Bulbs (and fittings) are same as license plate on VW Golf Mark 1 - I think that is the car you guys called the Rabbit ? Made from late 1970s to mid 1980s.
ps - non Amphi trivia, the later hot VW Golfs, the GTi and R32, are hugely popular in Europe yet were never officially sold or promoted in the US.
There were advanced plans in the late 80s to do that and a team of VW executives planned a presentation to the US auto press in New York in December 1988 to announce the project, sadly the flight they choose from Germany to New York was PanAm 103, the Locerbie flight, that was destroyed over Scotland by a terrorist bomb.
It caused such upset within VW that they decided to cancel the project and the US missed the chance to drive some iconic vehicles that might have slowed or even stopped the rise of the SUV.
pps - I was told all this by a VW exec I met at a motor show when we were discusing Amphicar and Harald Quandt, Harald was part of the family that owns BMW and a major investor in IWK, the company that owned Amphicar, his death in an aircrash in 1967 was a major factor in Amphicar finally running out of money and stopping production.