This is a St. Vincent OHMS, or ON HIS/HER MAJESTY'S SERVICE Cover.  This one was sent from Kingstown, St. Vincent to Clinton, Iowa in 1896 via Registered Mail.

What makes this little beauty really special is the fact that it was registered with a St. Vincent SG 47w, the 1/2d Green, and SG 56, the 4d Yellow.  These are valued at L30 x 5 on cover.

This item is over $100 USD so I will ship it using Priority Mail in the US, and Registered Mail overseas.  This is to ensure that it reaches you in a safe and timely manner!