This is a Ricoh BC-605D Vintage Bulb Flash Gun.

It's a hot shoe synchronization extending fan type  bulb flash gun, but can be used with cold shoes if you attach a sync cable.

Comes with Leather Case and Adapter to use capless bulbs which is stored inside the back of the body next to the capacity.  See photos.

It has a rather handy calculator on the rear which allows you to feed in the guide number of the bulb you're using and you can instantly see the aperture required for the distance of your subject

All you need to do is buy a 22.5V battery and some compatible bulbs and you're good to go.

Only selling because I'm whittling down my collection of bulb flashes and I like these so much with my Ricoh 519 I have two!