Two Bronica S2a 12/24 backs for the S, S2, or S2a. They both have their share of dings and scratches. One (#4) is in good working order with a darkslide. One (#5) is missing a darkslide and the counter isn't working properly, but it seems to work and maintain proper frame spacing as long as you keep track of how many frames you've exposed. I had that counter looked at by Frank Marshman, and he couldn't find a problem, so it may be something about the way it fits on my S2a body, and it may work for you, but I'm basically including it in this sale as a giveaway.
You could get another darkslide from www.kohscamera.com or wait for one on eBay or just dedicate it to a spare body where you don't plan to change film mid-roll, use the insert to pre-load a roll of film when you need to change quickly, or keep it for parts.
To insert or remove a Bronica darkslide when the back is detached from the camera, press the pin in the upper right hand corner of the back with a ballpoint pen or similar object.
I had five backs mainly for when I was using the Zone system with my Bronica, but now I usually use a camera that shoots sheet film for that, so I rarely need more than three, and these two can move on.
$85 includes domestic US shipping, a little more for foreign shipping.