[Milsurplus] "Chemical Alarm" on ebay.

[Facility 406]

Any ideas as to what this is?:

https://www.ebay.com/itm/860051593201

Seller thinks M42 chemical alarm, but if he bothered to look at the 
several being offered, they look nothing alike.

Solar panel, a wire, some loose rivets, nothing else, and no inside pics.

I'm wondering if it was a case for something, someone was trying to 
build into something else.

Any ideas?

Kurt