  The supernova remnant N 157B contains a pulsar and three distinct synchrotron
components with rather unusual properties. 1) A somewhat irregular elliptical
pulsar wind nebula (PWN) visible in both X-ray and radio wavelengths. The
nebula is quite symmetrical with an extent of about 10 X 5 parsecs but offset
along the long axis by about 4 pc from the pulsar position. It is apparently
the result of a short-lived injection of energetic particles, perhaps starting
at the time of explosion. 2) A very bright X-ray shock region located just
outside the pulsar position in the edge of the PWN. This is undetected in the
radio. We attribute this feature to a new burst of particles from the pulsar
suggesting there are multiple episodes rather than continuous injection. 3) The
beginning of a radio synchrotron shell on the southern side of the SNR where
thermal X-rays appear to arise suggesting that N 157B is starting to become a
composite SNR.
