This is a Horizontal Locking Shaft for the KT Locks used on Airstream trailers from years 1970-77.
Airstream Part number is 685198

The KT Story: KT locks were used by Airstream in the early 1970s on most trailers. Over the years, the design of the lock exterior and fit in the trailer has remained constant, but the interior has changed as the linking parts were modified. Airstream currently produces parts that fit the most recent version of the KT Lock, so some parts available today do not work well with older locks. Unfortunately, there is not easy way to determine whether the parts available today will fit in your lock or fit with modification. Of course, you can return any part that does not fit so long as it has not been modified, damaged or used.