Mine is rather easy....
I spent almost 25 years as an Artilleryman in the Royal Canadian Artillery, hence Gunner. As we always say once a Gunner....always a Gunner!
The 27 was one of the call signs I had as the Battery Seageant-Major. So Gunner27
My TKID is 71418, If you take the seventh, fouteenth and eighteenth letters of the alphabet you get GNR, which is the abbreviation for Gunner.