54 squadron Spitfire individual ID letter

My name is John and this is my first post on this site.

I am looking for the individual letter code for a Spitfire MK IA S/N R6707 that served with No. 54 Squadron that was shot down on july 25, 1940. The pilot was F/lt Basil H. Way. I have read that he was shot down by Adolf Galland, but can’t confirm this. I have surfed the web and came up empty handed except for the information above. If anyone has any idea of what the ID letter I would greatly appreciate it; I want to build a model of this particular A/C for a group build.

Thanks
JRW