I think he had an Alexander Henry 450 as well.
One thing I’ve found unusual is that for a man who gained quite the notoriety in his time, there are very few photographs of him.
I’ve closely studied the photos of Selous with rifles (maybe four total) and believe I know what rifles they are.
Of course, there is the picture of Selous with the Kori Bustards and his H&H falling block which I think is a 375 2-1/2” which was rebarreled to .256. Maybe replaced with a .256.
Then there is a picture of him with a large bore muzzle loader.
There’s a studio sitting picture in which he has a Jeffery Farquharson laying across his lap.
Another photo shows him with a rifle over his shoulder which looks like a late George Gibbs Farquharson.

There may be one or two others I’m forgetting.

I’m reading Selous’ Travel and Adventure in South East Africa and he mentions a number of his rifles in this book.