Shopsmith has several miter gauges that it sells. The version with the washer and screw are for the 505/510/520 tables with the t-slot.
If you have the older 500 then it has no t-slot so they sell a version with that doesn't have the washer. The whole bar is different as well, no place for the washer etc.
Now, the part 514377 is listed as the screw, the washer is 314376. The screw is $.96 and the washer is $4.96. Total of $5.92 then there is shipping........
I have one of these that has been modified so the washer can be turned and fit a non t-slotted table like on my older cast iron bandsaw and the 6" belt sander. This way it can do double duty. If you are interested to see that modification I can get a picture of it later.

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Ed