Perplex City Postcard

So far the Perplex City postcard has been found in these locations:

• Bologna Airport, Bologna, Italy
• Chapel Hill, NC, USA
• Cambridge, Cambs, England
• New York Public Library, SE Fifth and 40th, New York

Places searched:

• Liverpool, Merseyside, England
• Glasgow, Scotland
• Manchester, England

Theories

• The code below the Semacode means something. Working: Postcard Code
• The PCPS maze may have meaning.
• The PCPS maze is drawn by hand.
• Postcard Discussion on Unfiction.

Content

• Painting of Perplex City at night
• The pattern of lit and unlit windows of the building in the foreground of the painting is binary for "helloworld"
• Letter from Sente
• Semacode pointing to Perplex City (NOTE: Semacode is simply a Data Matrix ISO/IEC 16022 standard barcode containing a URL. You can decode semacode with any standard reader)
• Code of 221545484848465100503215 - Postcard Code
• A line "MC, Please expedite global release. S"
• A stamp with a maze and "PCPS" in the centre
• Text down the middle: "Despite heightened security Academy tours are still running twice daily from gatehouse twelve. Advance booking essential."
• A full Perplex City Academy crest.

My friends -

I need your help.
Cube - missing.
Presumed stolen.
Not enough room
to explain here.
Too risky.
Your assistance
will be rewarded.
More contact to 
follow - stay alert.
Yours in hope,

Sente

Puzzles

• Postcard Code

Images

Postcard - Front

Postcard - Back

• High Resolution Scans of the Postcard
  • Front
  • Back

Postcard 1

Postcard 2

Possible Sente Sig

Sente Sig Clear Version

Postcard Sig Clear

Composit of Sigs (by EclecticMunk)

Postcard Semacode

Edited Logo

Maze

Adjusted version of the front

Adjusted version of the back