http://blog.harriscyclery.com/custom...ed-freewheels/
If the OP wants disassemble the FW, it sure looks like a lockring to me, just like in the above link.
By disassemble , I'm referring to taking the cogs off to clean them and the spacers, not taking the body apart too, as this is only needed in rare cases and a sure road to anxiety for most people.
I do this with Sachs FW's all the time, also because there is a lube port underneath the cogs.