  We present the first laboratory experiments using a notch-filter mask, a
coronagraphic image mask that can produce infinite dynamic range in an ideal
Lyot coronagraph according to scalar diffraction theory. We fabricated the
first notch-filter mask prototype with .25 $\micron$ precision using an e-beam
lithography machine. Our initial optical tests show that the prototype masks
generate contrast levels of 10$^{-5}$ at 3$\lambda/D$ and 10$^{-6}$ at $\sim
8\lambda/D$, with a throughput of 27%. We speculate on the ``as-is''
performance of such a mask in the Hubble Space Telescope.
