OK, I got the big box of cams...Here is what I found
The top hat cams for the 500A and 603 and Touch and Sew 640 all use the same cams.... All the part numbers are identical!
The set for the Touch and Sew, even though the part numbers are the same, have a slightly different ring around the top hat. I will put one in my 500A and see if it works.. I am pretty sure it will as that is not the working part of the cam. The depth is identical, part number is identical and the shape and cut of the cam is identical.
I dont have an original set of the 400 series cams, but per the blog that was posted in a previous post on this thread, they are the same as the 500 series.
So, they are all interchangable between the 400, 500 and 600 series machines.
The 300 series cams are NOT interchangable as they are flat, with no top hat. I am looking for those as well for my 306.
JC