Judy,
The 66 is not a 66-16. The -16 has a stitch control lever with a back tack feature, yours has the old stitch length knob.
It is most likely a 66-6.
My info came from ISMACS here: {
http://www.ismacs.net/singer_sewing_...sses-1-99.html }.
purplefiend,
The 66
is threaded correctly for embroidery and darning. For regular sewing the thread goes under the thread regulator, for embroidery and darning it goes through the eye of it.
Joe