That requires a great deal of research! The letters in the corners give the plate position. The actual plate is going to require referencing specialty publications and getting into 'fly speck' philately. That involves looking for minor differences and scratches on the actual stamp.
On the One Penny Red, look in the grill design on the edge to the left of the profile. It is sometimes found there.
The letters in the upper and/or lower corners represent the row and column of the stamp on the plate.
The Queen Victoria, penny-red, plate 77, one penny stamp.
Plate 77 is a rare victorian postage stamp
Queen Victoria who was the Queen of England when the first Penny Black stamp was printed in 1840.
Here's a picture of the earliest English half-penny stamp. There were probably others later. http://www.stampwants.com/Great-Britain-58-Mint-OG-Fine-Sound-Plate-11-CV-110_QQitemnameQQ2836088QQidQQauctiondetails
There isn't any stamp that is called a penny purple. You need to describe the stamp - include country and if you can date and what is on the stamp.
A plate refers to the printing plate used in the press to make the stamp. The number is printed in the margins of a sheet. Collectors like to have four or six stamps with the margin intact and including the plate number. The post office uses the numbers to inventory the plates and fix errors.
Scott Number GB#1 was issued in 1840.
There isn't any stamp that is called a penny purple. You need to describe the stamp - include country and if you can date and what is on the stamp.
The One Penny Black had a silhouette of Queen Victoria on it.
The value of the 1910 1955 penny stamp value is one pound.
Depends on the stamp and the plate numbers. Since the 40's, many people saved plate blocks from their sheets of stamps. Many of them are very common and can be purchased for about 5 times face value. Consult a specialized catalog to find specific values.
British