Your lens likely has a Canon FD mount. The reasons are as follows:

• It has a breech mount. Canon FL/FD lenses are among the most well-known breech-mount lenses.
• The location of the linkages matches those on Canon FD mount lenses. Note there are two "pins" on the FD mount. One to "auto" control the aperture. The other to communicate the aperture position for aperture priority.
• The lens has screws that match those on known Canon FL/FD breech mounts. (Circled in red.) These screws fit into a notch in the FL/FD breech-mount lens cap. (Circled in blue.)

You can confirm the mount by attaching the lens to a camera with an FD mount.

If you'd like, you can measure the mount diameter to compare with a list of lens mounts (alphabetical, by-register, Wikipedia).

See Evolution of the Canon FD Mount.

Related Questions:

• What is the breech mount on this Chinonflex lens?
• What is this breech mount with three flanges and a single linking pin?

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The pin on this lens is not longer than the pin on any other FD-mount lens. It only appears longer because of perspective:

• The lens is being held with the front element away from the camera. Note the converging lines of the lens barrel.
• The camera is also being held at an unusual angle and position.

Here is the pin from a new-FD mount for comparison.

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It seems unlikely that not having a moving mirror would allow the Pellix to be able to take a longer pin. The mirror in FD mount lenses is above the aperture-control linkage. Whether the mirror is present or moving does not affect how long the pin can be.