THE DOGSMEAD PUZZLE

This is an interesting little puzzle -- a numeric crossword puzzle. The rules are simple:
All entries are positive integers, and no number begins with a zero (0).

It is said that only a genius can complete this puzzle successfully. There is no guess-work involved. The answers are obtained through sound reasoning and from the key information supplied.

The puzzle was invented when there were 20 shillings to the English pound.
1 rood = 1/4 acre, 1 acre = 4840 square yards, 1 mile = 1760 yards. One of the cross numbers is the same as one of the down numbers. One number in the puzzle (relating to something quite different) happens to be the area in roods of the rectangular field known as Dogsmead.

In what year was the puzzle invented?  
   
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ACROSS DOWN
  1. Area of Dogsmead in square yards.
  2. Age of farmer Dunk's daughter Martha.
  3. Difference between length and breadth (in yards) of Dogsmead.
  4. Number of roods in Dogsmead times 9 DOWN.
  5. Year when Little Piggley came into occupation of the Dunks.
  6. Farmer Dunk's age.
  7. Year of birth of Mary, Dunk's youngest.
  8. Perimeter (in yards) of Dogsmead.
  9. Cube of Dunk's walking speed (in Miles Per Hour).
  10. 15 ACROSS minus 9 DOWN.
  1. Value of Dogsmead in shillings per acre.
  2. Square of Mrs. Grooby's age.
  3. Mary's age.
  4. Value of Dogsmead in English pounds.
  5. Age of Dunk's firstborn, Ed, who will be twice as old as Mary next year.
  6. Square of the number of yards which is the breadth of Dogsmead.
  7. Number of minutes Farmer Dunk takes to walk 1 & 1/3 times around Dogsmead.
  8. See 10 DOWN.
  9. 10 ACROSS times 9 DOWN.
  10. Sum of digits in 2nd column plus one.
  11. Length of tenure (in years) of Little Piggley by the Dunks.