I just found this...."However, the Swedish association with the Spitfire goes back to 1939, an order for 15 MkIs being placed on 12 May of that year. With RAF deliveries taking precedence, this was rejected."
Looking around to see what's the difference is between a Mk.I and Ia, I found out that there IS no (apparently) difference between the two, that the (a) was invented, showed up later....
Actually it is true both Mk.I and Mk.IA were the same aircraft basicly. It is matter of nomenclature. The marking Mk.IA was introduced when the need for distinction of the variant armed with 8x .303 MGs from the version with the 20mm cannons in wings appeared. However it should be kept in mind that the Mk.I was still upgrading. So the early Mk.I had a little bit different appearance than the later one for instance.