The seal reads:
COLLEGII BROOKLYNENSIS SIGILLVM or Seal of the College of Brooklyn
MCMXXX or 1930
NIL SINE MAGNO LABORE or Nothing without great effort
And has a depiction of the tower behind it.
The seal is best read at this photograph's "all sizes" page.
The tower was initially called "the library", however the simple name
was eventually changed in honor of one New York's more famous
mayors, and is now named LaGuardia Hall.