just curious, and looking at old pattern pictures is sometimes difficult, but I don't think that one set of rings in the picture are tre-foils.
On left side just above the corner is the clearest, and to me it looks like ring~ring~chain~Ring joined to prev row~ch~ring joined to previous row~ring~ch joined to prev ch and to previous ring~ch~ring~ring (which is back to the beginning of the repeat.)
I took a good look at the original picture and can see that there is a chain between the two rings that is joined to Row 2, but that part was missing from the instructions. Here is the original image which I downloaded from the site,
I tatted Row 3 again but made some changes to the stitch count in the chains. I also added the missing link, but only guesstimated the stitch count since it was not given in the pattern.