F. Koeller & Co MAGNA Scissors

Hi there!
I recently bought these scissors and letter opener, and knowing nothing about them, did a simple web search, just to find /my item/ was listed on Australia's eBay for sale about a year ago (a tiny rust spot and a ding on the sheath confirmed it was the exact same). So, fascinating story, they were made in Germany, somehow went to Australia, and ended up in the U.S.!
But I haven't been able to find out anything about their manufacture.
They are stamped with the marks "Germany" and "F. Koller & Co" and "MAGNA".
Does anybody know when these were made? Can they be identified as an specific model?
All items are attracted by magnets so they must be some sort of ferrous metal, but the handles and the sheath have patina much like that of silverplate.
Any info would be appreciated!
Thanks! :)