That Serial # should date your gun somewhere between 1896 & 1904.
During that period Midland sold a variety of hammer guns made in Birmingham and a few cheaper guns made in Belgium.
I have a reprint of their 1933 catalogue and at that time their 'Best' Sidelock ejector sold for 50 ( around $77) and they still listed muzzle loading doubles for just over 3 (say $5)
In 1933, I think the pound was worth somewhere north of $4. By way of comparison, in 1936 a Churchill Imperial (what they called a medium priced sidelock) sold for 75 pounds in London.