Below are some scans of various revenue stamps & revenue documents to give people an idea of the interesting items that can be collected. I'll add more as time permits.
Scare high value "ONE POUND" revenue from St. Vincent (1882) with partial double overprint on the "ONE"
Aiport departure tax stamp from Egypt.
St. Vincent postage stamp used for revenue purposes on this Hotel receipt from 1948.
Modern (1978) St. Vincent postage stamp used to pay a fee on the back of a personal check.
One of the few surviving bill-of-lading documents from St. Vincent dated 1891. I have several hundred of these 1 pence stamps shown on this document, unfortunately they were all soaked off their respective documents, which is quite a loss to collectors. If in doubt, do NOT soak stamps off from envelopes or documents.