Here is the same stamp.
You may notice the letters in the corners are different. Each stamp in the sheet of 240 stamps had different letters. This was a measure to prevent forgery the Post Office used from the very first stamp issue on 6 May 1840.
A sheet had 20 rows of 12 stamps. Each row of twelve stamps would add to a shilling in postage. The twenty rows added to a pound.
The letters in the lower corner identify the position in the sheet. The letters appear in reversed order in the top corner. So, your stamp has 'corner letters' MF. This came from the thirteenth row (M). It was in the sixth position (F) in that row. The letter combinations ran AA, AB, …, AL, BA, …, BL, TA, …, TK, TL.
The stamp I post here is the penultimate (K) stamp from the top row (A)
Your stamp has an identifiable cancellation from office number 760. This was used at Sudbury in Suffolk.