Caroline,
When I was researching my 404 I came across that same comment about the 606. Seems there was two different machines with the same model number. I have no idea where I found that, but if I come across it I'll let you know.
I've seen three different SEWMOR model numbers; the 202 which is a 15 clone, the 404 which is a cross between the 201 and 66, and the 606 which has two versions.
Making a total of four. I'm partial to the Sewmors and want all four. Eventually.
Joe