Part of my research for my thesis on the 42nd Division has led me to researching Service numbers. I have a detailed database that covers the 1/5th to the 3/5th. These are some of the results.
The 2/5th and 3/5th battalions were tasked with providing drafts to their 1st line battalion, but this was also extended to the service battalions. Through my research, I have found at least 35 men (with service records) that were issued with four-digit service numbers. Disembarked in France on 27th July 1916. They were then transported to Etaples and administered by 1/5th King Liverpool Regiment. . This was a part of 30th I.B.D. The men were attached to their new unit, in this case the 18th battalion, before being transferred to their new unit. Almost all of the new service numbers start with 437 or 438, for example, 43744. From the 18th's war diary, 26 men joined in late July, followed by another 410 the following day. One interesting point is that in almost every case, the men were returned to their original battalion once the 18th was reduced to a cadre.
This is for the 5th battalion; I would presume that the same would have happened for the other 2nd line battalions.
