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

Speculation

• The code below the Semacode means something.
• The PCPS maze may have meaning.
• Postcard Discussion on unFiction.

Content

• Painting of Perplex City at night.
• On the Image of the building on the painting, the windows convert to "helloworld" from binary.
• Letter from Sente.
• Semacode pointing to Perplex City
• Code of 221545484848465100503215 - Postcard Code
• A line "Mc, Please expetite global release. S"
• A stamp with a maze and "PCPS" in the centre
• Text down the middle: "Despite hightened security Academy tours are still running twice daily from gatehouse twelve. Advanced 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

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