In 1914 the Territorial Force Battalions of the British Army, including those of the King's Own Royal Lancaster Regiment each had their own numbering system. When the Territorial Force battalions were created from the old Volunteer battalions the numbering started in 1908 with number 1 and worked upwards.
As the First World War continued and soldiers were transferred from one battalion to another within the same regiment confusion could occur over a soldier's number.
Adding the Special Reserve and Regular Battalions into the mix it could be possible that the same number could be used by four, or may be more, soldiers in the same Regiment.
In 1917 all the Territorial Force units of the British Army were re-numbered.
The re-numbering took place of all soldiers, including some who had died well before the 1917 re-numbering, on the assumption that a soldier posted "missing" may well be just that, missing, and may turn up as a prisoner of war, or may be even in a hospital.
The museum's collection contains a book which shows the four figure and six figure conversions for the 1st/4th Battalion, King's Own Royal Lancaster Regiment; and some information on both the 1st/5th and 2nd/5th Battalions, but sadly not a complete list for these two battalions.