Lang was one of the top London gunmakers. If it had remained in business would be in the same sentence as holland, purdey, boss and grant.
A little more history of something at the opposite end of scale at the end of this post.
The 10 bore and 12 bore express rifles where the every day big game rifle of 1870’s to 1880/90’s by which time the Nitro Expresses came into play.
This period of about 30 years you went from muzzle loaders, through breech loaders to modern high velocity smokeless powders. And your rifles went from bore guage black powder at speed of sound to 7x57 high velocity at twice the speed.
I suppose a bit like we have gone from telex and air mail letters that would take hours and days / weeks to arrive on the other side of the world to writing a note a portable device that you will read within seconds of me writing it.
When those guns were made your order would have travelled by horse, steam train and sail or possibly a steam ship across the Atlantic and couple of years later it would have arrived back. I suspect many of these rifles never saw much use - new technologies quickly came to the fore and they were obsolete. Many would simply been put away in their case, hopefully cleaned and well oiled, and put in the back corner of the gunroom of one of the many large country houses only to resurface many decades later when an heir needs to raise some cash to pay school fees or reroof the castle.
And the buyers usually had the money to keep themselves up to date - although plenty went bankrupt in the process.
Have you heard of Lang & Sons?
www.vintageguns.co.uk