Model 99 came in three various guises over the years. I think it was introduced in 1911 and around 1950 it was given a stitch length lever with backtak, not true reverse like model 201 or 15 but with a set stitch length in reverse. There were two versions of the reverse lever, and some alterations to the bobbin case and hook along the way too. I have an electrical 99K from 1934, with the the stitch length knob. In spite of what you might read or hear from someone, this is a smooth machine when cleaned, oiled and set up right. There shouldn't be much noise at all. Perhaps you can remember any look or feature when looking at the pictures on
this site. It's a much tougher model than the Featherweight, it will take on any job you can fit under the presser foot and it will do it for at least two or three generations.
From your description I think the old machine you remember might have been a model 15-91, the version with the potted motor. It's quite a sought after model among quilters and those who do free motion stitching. It's the only domestic model I can think of with this type bobbin case (much like Berninas), and it came in a version with a direct drive motor (no belt).
I found photos of bobbins
here, class 66 and 15 are the most common.
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