I think my 319W has been altered because I removed the needle for the first time and it compares to a 15X1 exactly. Also, it looks like the 15X1 that is in Cathy's post above dated 05/04/2013.
I put in a fresh 15X1 today and sewed a few blocks for the next TOGA since I have put this machine into a treadle base. It is sewing fine. There are no marks on the bobbin case. The decorative stitches worked great when I tested them out when I first got my machine.
My question is: Should I get this machine re-timed so that it uses the intended 206X13 needles or continue to enjoy it using the standard and plentiful 15X1's?
(PS: THANKS Cathy! I did a Google looking for "difference between 15X1 and 206X13 and this post came up with your pictures which is EXACTLY what I was looking for!)