It is an "autoportrait" selftimer with a curved mirror. After setting the timer, the photographer goes to his place and he can see his own reflection in the mirror.
Known numbers:
2817____Michel's collection.
3338____seen on eBay.
4314____David Tomlinson.
4881____Jacques collection.
4937____seen on eBay.
5086____PYC. collection.
5752____seen on eBay.
6114____seen on Molotok.
8083____imcphoto collection
8090____seen on eBay.
9944____Christian G. (Niko80)
10814___fotomuda
11508___seen on eBay.
12341___seen on eBay.