The Tower of Art

Year One:  Green

Depicting the Unseen University Tower of Art amid its scholastic environment.  A most unusual stamp with reports of transfiguration within the engraving.  All are subject to in line perforations (coarse) cut.
The TOA has been printed in at least three separate runs.  The first run can be distinguished easiest by the lack of any printing in the gutter (the edges of the sheet) while the second version does have printing.  The latest print run includes the new sports and has an upside down falling man in the picture in the gutter.
The left side of the gutter reads: ANKH-MORPORK ~ THE YEAR OF THE PRAWN while the right side reads:  TEEMER & SPOOLS · TOWER OF ART ~ ONE DOLLAR
  Dimensions:  20 mm x 100 mm
  Released:  July 2004
  Withdrawn:  December 2005
  Number released:  35 000 (10 000 of which were used on Waterstones covers).
 Original cost:  
   Individual stamp: £1.00  SHS-RW0007-Ab; SHS-AM0007-Aw
   Rarity: 10 400
The sheet of this stamp was NOT available for general sale.  Only one sheet was ever sold via an auction to raise funds for Boxing Day Tsunami disaster relief.  SHE-AM0006-Aw

Sport: Falling Man

Features a man falling down the right side of the tower.  Stamp located on the right top corner of sheet.
SHS-RW0007-Bb; SHS-AM0007-Bw
Rarity: 650

Sport:  Splashing Man

Features the splash of the man hitting the water of the lake below the tower.
SHS-RW0007-Cb; SHS-AM0007-Cw
Rarity: 650

Sport: Falling Man: One horizontal bird

As for Falling Man sport but the top bird to the left of the tower is more horizontal than the original.
SHS-AM0007-Dw
Rarity: 62

Sport: Falling Man: Two horizontal birds

As for Falling Man sport but both birds to the left of the tower are more horizontal than the original.
SHS-AM0007-Ew
Rarity: 40

Sport:  Splashing Man:  Bigger splash

As per original splash, but the size of the splash is higher and the ripples in the water differ.
SHS-AM0007-Fw
Rarity: 60

Sport:  Reversed Weathervane

The weather vane on the building to the right of the tower in the background is pointing the opposite direction.
SHS-AM0007-Gw
Rarity: 60

Year Two:  Blue/ Red

Red and Blue tints on a white background.
  Dimensions: 20 mm x 100 mm
  Released:  February 2006
  Withdrawn: February 2007
 Original cost:  
   Individual stamp: £1.00  SHS-AM0047-Aw
   Sheet of 18:  £18.00 SHE-AM0033-Aw
   A5 artists proof sheet of two:  

Sport: Upside down TOA

In a style similar to the famous roundworld stamp with the upside down plane, the TOA is upside down relative to the border.
SHS-AM0047-Bw
Rarity: Unknown.  Not located on sheet.

The Tower of Art:  Brown

Like the green Year One TOA but in shades of brown.  Depicts the Unseen University Tower of Art amid its scholastic environment.  Only available to the first 150 purchases of the Cut-Out Unseen University from The Cunning Artificer.
  Dimensions: 20 mm x 100 mm
  Released:  September 2006
  Withdrawn: December 2006
SHE-AM0007-Hw
Rarity: 150

Year Three:  Rainbow

The 'fountain' print Tower of Art stamp for the year of the Reversed Ptarmigan. Shades of brown, green and ochre. Depicting the Unseen University Tower of Art amid its scholastic environment.
  Dimensions: 20 mm x 100 mm
  Released:  February 2007
  Withdrawn: February 2008
 Original cost:  
   Individual stamp: £1.00  SHS-AM0077-Aw
   Sheet of 18:  £18.00 SHE-AM0061-Aw

Sport: Darren (red shades)

The top and bottom of the stamp is in shades of red (ie, the ochre from the bottom is missing).
SHS-AM0077-Bw
Rarity: Unknown.  Not located on sheet.

Sport: Jonty (green shades)

The stamp is in shades of green (ie, the red from the top is missing).
SHS-AM0077-Cw
Rarity: Unknown.  Not located on sheet.

Sport: Noggin (ochre shades)

The stamp is in shades of ochre (ie, the red and green are missing).
SHS-AM0077-Dw
Rarity: Unknown.  Not located on sheet.

Year Four:  $1 TOA Violet/ Chocolate

The new Tower of Art one dollar stamp for the Year of the Three Roses, in shades of chocolate and violet.
  Dimensions: 20 mm x 100 mm
  Released:  February 2008
  Withdrawn:
 Original cost:  
   Individual stamp: £1.00 SHS-AM0117-Aw
   Sheet of 18:  £18.00 SHE-AM00

Sport: Mirror image water

The water reflections below the tower are the mirror image of the common
SHS-AM0117-Bw
Rarity: Unknown. Not located on sheet.

Sport: Mirrored buildings and water

The water reflections below the tower, the background buildings and the TOA itself are the mirror image of the common (birds are unchanged)
SHS-AM0117-Cw
Rarity: Unknown. Not located on sheet.

Year Four: 50P Green

The new smaller Tower of Art stamp as mentioned in 'Making Money'.  In shades of green.
  Dimensions: 20 mm x 93 mm
  Released:  February 2008
  Withdrawn:  
 Original cost:  
   Individual stamp: £0.75 SHS-AM0118-Aw
   Sheet of 18:  £18.00 SHE-AM00

Forgery:  Jenkins forgery variant