A Saab 99 prototype is exactly what it is!
As far as the 'PA 0000' goes that is just a made-up Swedish registration number from the period.
In those days Swedish registrations were black on white (as they still are...) and were based on major Swedish towns or counties, which had single-letter codes allocated, I believe, geographically starting from Stockholm which had 'A' and 'B'. Gothenburg and Bohuslan county had 'O' and Alvsborg county, which is where Trollaetan and the Saab factory is situated, had the next letter along, 'P', being just a few miles north-east of Gothenburg. In 1956 some authorities were given a second letter as all their possibilities using only 1 letter (and up to 5 numbers) had been used up! Hence Alvsborg got PA in addition to P. All that has, of course, changed, as it has in most countries, with all numbers now allocated centrally so there is no way to recognise where a car comes from any more.
