I have no idea when the first 99 was electrified. Both of mine were made in the mid-50s.
That little spring is a brush spring. Without the cap the motor will not run properly if at all. I believe Sew-Classic sell the caps and brushes. I'd buy a pair of both.
They also have the springs and screws for the slide plate.
You might try Thayer Rags for the handle on the case top.
Since I don't like working with chemicals, I'll be skipping this process. For me, just the use of the sewing oil to pretty up the machine works well enough to make me happy. The costs is lots less too.
Nancy, I still have never used my Free that I picked up for free.
On that same day that I picked up the Free, I picked up a Graybar. After researching Graybar and National, I realized that the one machine that I couldn't identify on CLs was the National Two Spools. That machine had sat for at least a month before I picked it up. I was too intrigued with the Two Spools that the Free got moved aside. I used the top of cabinet to hold sewing items and the only bobbin that it came with went to the Singer VSII. Interesting how one machine can lead you to another machine. :)
Glenn, You might have not seen this thread/post. Looks just like your MW machine. One of the photos show the threading.
Thank you Vintagemotif