Here a comparison with a H&H.500express made in 1884

The Cogswell & Harrison was a slight larger dimensionwise than the H&H. A little thicker chamberwalls, wider breech.

When saying all these were made in Birmingham might be true but definatly by different people or companies. If one see the images the lumbs , locking and foreends differ.

Marking in the forend of the Cogswell