This is a Jamaica Underpaid Cover sent to Barbados on 21 July 43, censored in Jamaica with British tape 1:1 5610.  It also has a Block of 4 Barbados Dues added onto it.  These are SG D2.  It was cancelled on 12 Aug 43.  This is an absolutely amazing item!

This item is over $100 USD so I will ship it using priority mail in the states, and Registered Mail overseas to ensure that it arrives in a safe and timely manner.