Hi,
Was your father involved with tanks? I think these are not his army numbers but instead refer to the 7th and 1st Battalions of the Royal Rank Regiment which I believe, were serving in Korea in the early 1950s. I feel sure his army number would have remained unchanged during his service and would have been allotted to him when he joined. If this was in the early 50s I think his army number would perhaps be of eight digits. By 1955/6 these were commencing 23------
Hope this helps.