1. Item 1 comes from the original printing. There was a shallow roulette mark for folding on the reverse, which did not show through the front.
2. The booklet containing Item 1A was produced with two different UPC codes on the reverse, but the stamps are indistinguishable as singles.
3. The rouletted pairs come from the 2nd and 3rd row of each booklet.
4. The CBN printings and AP printings are distinguishable as single stamps,
   as are the different different paper varieties. See Identifying the Different Printings of the 2003-04 Rate Definitive Stamps and Paper Types.
   

1. The booklet containing Item 1A was produced with two different UPC codes on the reverse, but the stamps are indistinguishable as singles.
2. The rouletted pairs come from the 2nd and 3rd column of each booklet.
3. The CBN printings and AP printings are distinguishable as single stamps,
   as are the different different paper varieties. See Identifying the Different Printings of the 2003-04 Rate Definitive Stamps and Paper Types

1. Item 1 has the stem of the maple leaf seed protruding past the right printed edge of the stamp, while on item 2 it stops at the edge of the design.
2. different shades exist for item 1, especially the red/orange colours.
3. Two printings of item 2 may exist, but this is yet to be confirmed, as different intensities of shades exist for both the blue and green colours.

1. The booklet containing Item 1A for both values was produced with two different UPC codes on the reverse, but the stamps are indistinguishable as singles.
2. See  Paper Types for differences.

See this series on Robin Harris's Website