A lens is glass in a barrel. The price sits in the invoice and in the coating, the damage sits inside as a haze, long before anyone enters the house. In the overview Security for collectors it belongs with the camera, as its own line.
What gets ruined without a thief
Fungus likes damp and darkness without air exchange. A case in the basement is known for that. Dust under the lens comes from opening it in the wrong air, not from lying there with both caps on. You store dry, with caps on, and you air the stock on a rhythm you keep, instead of forgetting the case for ten years.
When someone comes
A full case has a handle. It goes in one move. Expensive fixed focal lengths do not lie in that one case by the door. They lie in the cabinet or in a second container that is not labeled like "the camera equipment".
The folder
Each focal length a line, with serial number and receipt. A scratch on the front element is held in the photo before you later confuse it with burglary damage. The policy sees four lenses if you send four lines.