pic: 1675 Teaser #3

This is too cool of a picture NOT to post…can you figure out what its for though?? All will be revealed on Sunday at the Team 537 pre-ship competition.

Is it a shaft your trying to spline with a bridge port?

Real splining is done with a hob or a shaper.
This shaft is to long for a shaper.

My guess is that those slots are to keep your arm from rotating.