by KayFarndon » Wed Mar 05, 2014 9:03 am
I have searched four Internet sites which deal with British military abbreviations and there is nothing for the collection of letters you have stated.
I can offer the following, although they are only speculative.
I found The King's [Liverpool Regiment] active during WW1.
For RLM, perhaps the 'R' is regiment, the 'L' Liverpool, or the 'M' military?
Hope it gives you some ideas.