Hi,
Sa far as I know, numbers were issued in blocks to each regiment or corp. This was the case post WWII. I should imagine the same before the wars.
Peter
no this wasn't the same in the years previous
before WW1 regular and territorial army regiments used 1-9999 and recycled them when they reached 9999
along with the new army units in WW1, they used batches of 5 figures numbers, but these would be duplicated in other regiments
in 1917 the territorial army battalions were re-numbered in an exercise that allocated blocks of 6 figure numbers to each regiment, which then were sub divided into battalions, this is one of the first time that you can identify a soldier's battalion by his s/n ( but not his regiment)
cheers
chris