Great Britain Envelope- Queen Victoria

I have no catalog for foreign envelope stamps. I am hoping someone might be able to help me identify this envelope (or wrapper) stamp from Great Britain. Has to be before 1901 as Edward VII ascended the throne in January 1901 and this is Victoria and the postmark appears to be 1894. I love the shape of the stamp as it is neither square of circular but oblong. Hope someone can put a catalog number and relative value to it. Thanks to everyone.

This is a cut-out (cut square) from a postal stationery envelope issued in 1892. The envelope came in two sizes. A recent British catalogue lists the complete envelopes as $5.00 and £7.50 used and suggests 10% of the cheapest usage for a cut-out, so 50p in this case.

When you put the 50p against the dollar, that makes the stamp worth about $900US (haha). Again thanks for the information, that is what is most important for me. I have no way to identify the world envelope or revenue stamps.