This is a genuine, Arri manufactured, Arri Straight or Bayonet Mount to PL Mount Adapter.
Besides being machined with extreme precision, the benefit of this adapter is the tab located inside the lens mount bore. That tab engages the focus mechanism in lenses like the Arri straight mount Cooke Speed Panchros, or early Arri Straight Mount Zeiss prime lenses, where the focus barrel rotates inside the lens mount bore. Without that tab, you will not be able to focus those lenses.
You can buy used or newly made copies of this PL mount adapter on the web, but many buyers are disappointed by out-of-spec dimensions of the tab or bore, making that copy unusable with their lenses. This is the real deal genuine, Arri manufactured adapter, guaranteed to work with your lenses. The key surfaces, on the front and back of the lens mount flanges are not turned in a lathe like the knock-off copies, but rather precision ground with a surface grinder to exact dimensions.
If you have the desire to have the smooth "look" of the Cooke Speed Panchro lenses with your Red or other PL mount digital camera, without the expense of remounting all your lenses, this adapter is a must-have.
The adapter is in excellent like-new condition and comes with a leather case.
Price: US Sold, FOB Los Angeles, CA.
Here you can clearly see the tab that engages the focus barrel of Cooke Speed Panchro or early Zeiss Arri straight-mount lenses. Also visible is the mechanism that engages and holds the straight or bayonet mount lenses firmly in the adapter bore.
Here you can see the red index marks for the focus scales on the Arri straight or bayonet mount lenses, when fitted in the adapter and mounted on the camera.
The adapter is easily and instantly removed from either an Arri straight mount or Arri bayonet mount lens by squeezing the two tabs on the back of the mount, one visible here at the 4 o'clock position. For straight mount lenses, squeeze the tabs and simply pull the adapter off. For bayonet mount lenses, you squeeze the tabs, releasing the bayonet ears, rotate the adapter counter-clockwise, and then pull the adapter off. It goes on the lenses just as quickly, making lens chagnes very fast.