Quote:

---

As I understand, the Lee Metford/Enfield sporting rifles that were manufactured by BSA and LSA, by patent law, had to recognise Lee Speed's patents and be so marked.

Patents were pending for a period of fourteen years. Any BSA or LSA sporting rifle that was made before the First World War would be marked Lee Speed.
The Great War happened and all manufacture of sporting rifles ceased as full attention was given to war production.
When the war was over and sporting rifles were made again, the patents had expired and so no longer were required to be marked.

So,

As I can see no LEE-SPEED PATENTS banner, which is quite a distinct to marking to see, I would confidently date your rifle post 1918.
In which case it will likely have been regulated for Mk.VII ammunition with a 174 grain bullet..

---