This is a cylindrical sterling silver case hallmarked London 1903.

It has the silversmith's stamp "G.H.J." for George Henry James & Co. One of the stamps is quite rubbed.

Such cases are sometimes known as "roundlets", possibly because they are small and round (at least in one direction), or possibly referring to an old term for a small barrel. 

They could contain gadgets such as picnic cork screws, or, as in this case , carriage keys.

The case unscrews to reveal a square section gilt key. This can be pulled out and rotated to lock into position and the case/ handle screwed back together.

There are two small dings to the silver near the join

Dimensions : Length 3%frac12;" (8.8cm) 
Weight : 2oz (57g)

Ref : Silver Carriage Key