This 150 year old conical flask has a solid silver bayonet or captured cap at its narrow end.

The seal is waterproof ( and port-proof, brandy-proof, whisky-proof etc)

It is hallmarked London 1872, the silversmith's stamp is only partly visible - possibly "E.C".
The top of the cap is monogrammed, this is not easy to read
The flask is handblown heavy crystal

The mahogany coloured case is lined with doeskin or chamois. 
The wide girth strap is attached so that the flask will sit on the near-side of the saddle. 
The case closes with a billet fastening and it has a top strap which attaches the flask to the D ring of the saddle.

Dimensions :
Length (of case): 9⅞" (25cm)

Weight 597g ( 1lb 5oz)