From 1908 The East Surrey Regiment fielded a 3rd (Special Reserve) Battalion and a 4th (Extra Reserve) Battalion, both these battalions being the natural heirs of the 3rd and 4th Militia Battalions, respectively. Men who had served with these militia battalions and who wished to complete their service with the newly formed Special and Extra Reserve battalions, retained their old militia numbers. Both of the militia battalions had operated separate number series and these series continued in use with the Special and Extra Reserve battalions into 1915 (and possibly beyond, although my database peters out then).
When Britain went to war in 1914, the East Surrey Regiment created two additional number series for men joining the 3rd and 4th Battalions for wartime service only. These two numbers series, one for the 3rd Battalion and one for the 4th, both started from 1 and both were prefixed SRGS or SR/GS or SR/GS/ES (and probably a good many other combinations as well for that matter). The letters stand for Special Reserve General Service East Surrey.
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