4.—(1) Any variation in–
(i)a dimension (other than as to the height of a letter) specified in any of the diagrams in Parts II and III of Schedule 1; or
(ii)a dimension as to the height of a letter specified in the diagram in Part III of that Schedule,
shall be treated as permitted by these Regulations if the variation–
(a)in the case of a dimension of less than 10 millimetres, does not exceed 1 millimetre;
(b)in the case of a dimension of 10 millimetres or more but less than 50 millimetres, does not exceed 10% of that dimension;
(c)in the case of a dimension of 50 millimetres or more but less than 300 millimetres, does not exceed 7½% of that dimension; or
(d)in the case of a dimension of 300 millimetres or more, does not exceed 5% of that dimension.
(2) Any variation in a dimension specified in any of the diagrams in Schedule 2 shall be treated as permitted by these Regulations if the variation–
(a)in the case of a dimension of 300 millimetres or more, does not exceed 20% of that dimension; or
(b)in the case of a dimension of less than 300 millimetres, where the actual dimension exceeds the dimension so specified, does not exceed 30% of the dimension so specified, and where the actual dimension is less than the dimension so specified, does not exceed 10% of the dimension so specified.