Anyone? What year(s) was Kenmore 1431 sewing machine sold?

Look what followed me home tonight. Okay, it didn't exactly follow me home. I saw an ad on Craig's list and went to look at it earlier this evening. When I plugged it in and ran a few stitches, well, it purred and the stitches were beautiful - almost as if it had just been tuned up. The price was right so hubby hauled it home for me. Along with an old thread storage chest (filled with thread, needles and bobbins) and a bag of cotton fabric. Most of the thread is too old to be of any use, but I'll hang onto the wooden spools of thread for decor in the sewing studio. The machine is an older one that folds away in its cabinet. Not as old as the one that I foolishly tossed years ago but older than the Kenmore I purchased in the mid 1980s, which I still own. As you can see, the cabinet is in rough shape visually, but it's still quite sturdy. The bobbin is located underneath the machine. And if you look really, really close, the middle of the needle plate slides out. That&