This black and white silver-gelatin photograph is showing “silver mirroring”, which is when the silver particles in the image degrade. From certain viewing angles, the mirroring is not noticeable, but from other angles it is VERY noticeable. This particular photograph was dry-mounted to a piece of foam-core board, and also matted, both of which probably contributed to the mirroring. You can read more about silver mirroring in photographs here.