Supplements for 1922, 1923 and 1924 of the NPS are printed as Supplements to Volume 17.
“……In the interests of economy, the Council has decided that the Supplement shall be published yearly in book form, but not be reprinted in the subsequent volume of the Stud Book.”
Volume 18 of the NPS was printed in 1924

Volume 18 of the NPS (1922-23-24) is the first volume not to incorporate annual supplements.
Annual Supplement (1922) to Volume 17 of The National Pony Stud Book.
conditions for entry.
Polo and Riding Pony Young Stock.
Age. – Colts and Fillies not over three years (a Pony reckoned to be one year of age on the first day of the year following that of its birth).

Qualifications –
(a) By an entered sire and out of an entered or registered dam.
(b) By a Thoroughbred, Arab, or Barb sire and out of an entered dam.
The later qualification is a temporary measure designed to overcome difficulties provoked by the Great War.

Note – The term “entered” applies to entries in the National Pony Stud Book (including the Supplement).
The term “registered” applies to entries in the “National Pony Approved Mare Register.”
The term “Thoroughbred” signifies entered in the “General Stud Book.”
The term “Arab” signifies entered in the “Arab Horse Stud Book.”
The term “Barb” signifies entered in the “Arab-bred Register”

Colts and fillies in this Supplement for Young Stock have the same Stud Book value as all entered Stallions and Mares (four years old and upwards). All measurements of young stock given in these pages are those supplied by owners of the ponies concerned.
The Eighteenth volume of The National Pony Stud Book
“ …… As regards the Polo gelding section the Council have decided that this section will in future be deleted as having no Stud Book value. ……… The Society this year made a new departure by holding, by the kind permission of the Ranelagh Club, a Show and Sale on April 24th …….As already announced, the annual Supplements will not be reprinted in the Stud Book, but will continue to be issued separately. ……. In the hope of keeping in touch with the produce and the performances of registered Polo Mares exported to the Argentine, the Council have appointed ……
Volume 19 (1925, 26 and 27) of The National Pony Stud Book.
Volume 20 (1928, 29 and 30) of The National Pony Stud Book
As will be seen many changes take place over the years in the production of the, “Stud Books.”
I have tried to note some of the more important ones.