P14 stock brass disk unit abbreviations

I recently acquired a Enfield P14 manufactured by Eddystone around May 1917( serial # 556xxx). The brass disk in the stock is marked H E R over 46. I believe the 46 is a rack number but can anyone advise what the H E R is an abbreviation for? Thanks for any assistance.

A photo is preferred as the unit can change with and with out periods between the letters and the height and spacing also has meaning.