I've looked through ebay, manuals, etc. and am not able to find an image/explanation for this Rolleiflex accessory. The camera was purchased at an estate sale. I also purchased a Weston light meter.
The accessory is pictured in the upper right hand corner of the photo, it has an "HR" emblem on the front. It also came with an electric cord that affixes to the front, pictured in the second photo.
It looks much like the selenoid that was attached to the shutter releases of the Speed Graphic family of press cameras. They were used to sync with electronic flashes, I wonder if this is something similar?