The mystery item is the top part of a temporary structure that will house the items. Why enclose them?

After all they have been subject the elements for the last 60 plus years. My guess would be they plan

To do something that requires this, like maybe sandblasting all the old paint off and repainting it?

I am sure they need to have this enclosed to do this. In the structure to the left, is

Visible a portion of the tower and the yellow is the light tower. next