Samuelson's inscription (spelling correction):

WAKE UP
YOU TAX AND
BOND SLAVES.
A POLITICIAN IS A BIRD
THAT GETS IN ON THE TAX
PAYORS (PAYER'S) POCKETBOOK FOR A FAT
RAKE OF (OFF) AND HIS FREE KEEPS.
HE LEADS YOU BY THE NOOSE
WITH ONE HAND(.)  WITH THE OTHER
HE DIGS IN YOUR POCKET.
A FRIEND OF THE BANKER AND BIG 
BUSINESS (,) WHY?

Interpretation:

"Rebel against the politicians.  They are like birds, flitting to and fro without so much as a care about you, the tax payer.  Politicians sponge off of us - the taxpayers - who are powerless to resist paying any taxes they levy.

Politicians are in league with bankers and big business interests to get our money.  It defies logic that this is so."

Send in your own interpretation.