" The guild in Schaffhausen (canton Schaffhausen) had a successive line of wardens who served in an unbroken line from 1577 until the mid-1850s. The last warden of the Schaffhausen guild would eventually become synonymous with Swiss silver: Johann Jakob Jezler (1796-1868; Master 1822)."
I can't find any Warden's Mark from 1620, but it is possible that the hallmark on your spoon is a predecessor to the Jezler hallmark, so you might have a piece of authentic Swiss silver from 1620, is that possible?
Of course, when you see a "pin-prick" or "pointillist" date and initials inscribed on a spoon, you would have to think about Denmark as well, so I can't rule that out either, but I was immediately struck by the similarity between your hallmark and the hallmark seen on Jezler (who was the last warden of the Schaffhausen guild, so is it possible that the hallmark on your spoon has something to do with the Schaffhausen guild circa 1620....? )
I'm thinking about Switzerland and Denmark right now, hope that helps, hope it isn't a wild goose chase