In Part 1, which covered the years 1863 to 1869, if you excluded the years 1863 and 1864, the
remaining years follow a similar pattern with the die numbers starting at 1 each year and
seemingly completing a range. After 1869 the die numbers used do not follow any pattern with
different types of half sovereign being minted in the same year, some bearing the same die
number although they are different varieties of half sovereign. Using the Spink reference
numbers I will detail which coins appear in which years and the die numbers that have been
recorded to date. All the different varieties will be fully explained after the details for the 1871
die number half sovereigns have been given.
A Study into Die Numbers Found on British Half Sovereigns in the Period 1863-1880, Part 2 1870-1875 – Brian Unsworth LLB
BNS Research Blog 
The author of this article is unaware of recent research published at the end of last year in the British Numismatic Journal 2024. The article “Victorian Die Numbers: Their Purpose and Their Demise” (pages 189-211) by Howard Hodgson gives a comprehensive explanation as to why die numbers were introduced in 1863 and why they ended in 1880. Hodgson’s article also undertakes a review of numismatic literature published over the last 150 years, pointing out that many inaccurate accounts have been offered as to the reasons why die numbers began but, equally, that several correct versions have also been written. Brian Unsworth’s article on die numbers and half-sovereigns has been written without reference to any of the previous research on die numbers and offers speculative and inaccurate explanations. It should be revised to take account of the most recent research.