Mbogo,
To add just a little more:

The W&C Scott serial number range started as you’d expect at ‘one’ in 1865 & by 1868 they’d got to about 1000
57000 took them up to 1896

Following the merger in 1897 it seems that the Scott serial number range became the dominant one for sporting guns (not revolvers/pistols) however several times between 1897 & 1940 blocks of numbers within that range were allocated just to ‘Scott’ branded guns. Generally speaking the post 1897 P. Webley branded guns used numbers from the normal number range. A friend has a P. Webley sidelock shotgun that was made around 1905 & has a serial number of just over 70000 (which is in the normal W&S range).

Your rifle as 470Rigby points out must have been made no later than 1904 due to the proof marks. If your rifle was a W&S made but P. Webley branded gun then it should really have a number between lets say 57000 & 68000 (1897 to 1904). Seeing that it’s only number 10000 I think it must have actually been made by P. Webley just prior to the merger & then ‘over-stamped’ by W&S at a later date.

I assume when the merger happened P. Webley had a quantity of guns in stock either finished or part finished (with P. Webley serial numbers), it would be natural for W&S to sell these with perhaps the addition of the new W&S trade mark stamped on them.

I wish I could remember where I’d seen the P. Webley serial numbers published – I’ll find it eventually when I’m looking for something else!

Regards
Webley