The two LSP doubles I have seen are the only ones I have seen so marked. It is my theory these doubles were nmade for India where Hill and Jungle shooting would be done, thus you had a bbl sighted in for 50,100,200,300, and 400 yards for "Hill" shooting and a double bbl sighted to 50 yards for Jungle shooting of DG.
The 400 was a very popular ctg for India, especially after @ 1905 when the British banned all 458 bore rifles and pistols from India and the Sudan.

It makes perfect sense, as usually the right bbl on a double gets the most use, and the rear trigger is the best one to use when making precision shots, as it feels better in the grip, and there is no chance for a double [shooting both bbls] when using a finer finess hold for a long shot.

London Sporting Park Ltd was a shooting school in Herndon, London. The doubles looked to be made by Webley, the same makers for many Army & Navy doubles.

The LSP Ltd people appear to be pretty savy to me.

I plan to sight the scope in for the left bbl, and use it that way for precision shots at a distance or on smaller game, or even when shooting through a hole in the brush up close.

I woulds rate this LSP and the Army& Navy guns I have seen to be the equal of ANY British double as far as the craftsmanship of the rifle itself is concerned.
Of coures higher grade doubles have prettier wood and finer engraving , but these rifles look to be as well "Built" as ANY other double, regardless of the name on the gun.

I like this LSP double so well that I drove all the way to @ Spokane to look at its twin [well, I did have a bear hunt planned in Montana], and I would have bought it for sure but it was a pretty rough rifle.
I was hoping it would be at least as good as mine as I would love to have a twin to it.