It looks like a typical studio portrait from the early decades of the 20th century to me. The olive tone is likely a characteristic of the paper used and not toning. I would suspect that it is a contact print made on a standard silver-gelatin paper of the day.
The metallic sheen you see is called "silvering out," and is a patina that forms from the silver in the image as it starts to degrade somewhat. Usually this is due to atmospheric contaminants or less-than-adequate processing.
There are lots of postcards and portraits from this time that now look a lot like your photograph.
Hope this helps some.
Doremus Scudder
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