Hector:

None of the marks present are those of Thomas Ketland. The crossed sceptres you see are the Definitive Proof and View marks of the Birmingham Proof House in use from 1813 to 1904. At the establishment of the Birmingham Proof House in 1813, the new marks were patterned after Ketland's private marks, hence the confusion.

In your second photo, left to right, are the View Mark, bore size, and Definitive Proof Mark. From 1855 to 1887, the British Proof houses marked the bore size of rifles as gauge, not decimals of an inch. The "38" is gauge, which is .500. The "No. 2 Case" certainly suggests .577/.500 No. 2. The only way to really tell with a rifle like this is to slug the bore and make a Cerrosafe chamber cast.

Your gun was proved in Birmingham between 1855 and 1887, although obviously much later than 1855. The .577/.500 No. 2 was introduced sometime prior to 1879.