Illustrated below in descending order are illustrations of the watermarks found on the definitive postage stamp issues of five British Monarchs from Edward the 7th to Queen Elizabeth the 2nd. The fist illustration is the "Large Imperial Crown" used on the definitives of Edward the 7th.
The second watermark is the "Royal Cypher" (flowing script) "Simple" and "Royal Cypher" "Multiple" two varieties of watermark used on the definitives of George the 5th. The watermark was a small crown over G v R and this was impressed only vertically in the simple cypher but spread over the surface of the paper in the multiple. The multiple is illustrated below.
The third example from the definitives of Edward the 8th in "Block Cypher" (straight line script) in multiples was a small crown over E 8 R. The only watermark used on Edward the 8th definitives because of his short reign.
The watermark used for Queen Elizabeth the 2nd was a multiple block cypher with a crown over E 2 R. Illustrated below