I have a used Ikelite DS51 strobe available for $200. It was part of a setup that I purchased but don't need.
Externally, the strobe is in decent shape. There is a crack in the battery door, although this can be replaced for about $10. It doesn't seem to affect the integrity of the door. Also, there was a battery leak in the internal compartment. I've cleaned it out the best I can, however, it's not perfectly clean. The internal part of the bulkhead is in good shape and doesn't show signs of corrosion.
Includes: box, strobe, metal bulkhead cap, ball adapter, and diffuser. (sync cord not included)
Shipping & Paypal fees not included.
Photos: https://drive.google.com/open?id=1vWTH2qNJCMupjRh9t9VrDr7gK8d5Qe4h
