Perhaps 15,000 1923 halfpennies exist.
Perhaps more than half of them show extensive die cracking, especially through the circumferential lettering.
I guess this is one of the main reasons why so few exist, and most of the 1923 production was completed with 1922 dies.
The fact that only 15,000 coins were struck suggests that a single die was used before it failed completely.
Perhaps that is not so, and a fault in the technique for hardening the die(s) was responsible.
Hence the question:
How many dies were used for the production of the 1923 halfpenny?
Is there any published research (perhaps relating to die variation) that may help answer this question?