Hi mate,
It is possible that it was a typing mistake.I went through some books about the Finnish AF but I haven't found any infos on thc CL plane.So I think it should be GL what stans for Gloster Gladiator figter.It is much possible because the tactical sign of the unit presents a fighter squadron.Additionally I uploaded ( I think all ) codes of used by FAF aircraft during WW2.It can come in handy.