Silver reflections on bw film?

[LomoSnap]

I recently discovered that a section of the film I developed, which was outside the film bag and not enclosed within it,
was emitting a shiny silver reflection. The part inside the film bag was perfectly fine.

I would like to know what caused this silver reflection.

 

[koraks]

At first glance your film looks like it may not have been fixed completely. I base this on the silvering that apparently also exists on unexposed frame edges, where no silver should remain at all after processing.
There's also the possibility of 'silver mirroring' due to environmental conditions and aging: https://www.conservation-wiki.com/wiki/PMG_Silver_Mirroring But this is more common in old samples.