What part is this thing missing?

mardi 3 mars 2015

I ask the forum's help in restoring this tool to its former greatness.

I have more than a few T-bevels with this style of fastener.

bevl 007.jpg

But this earlier example is missing a nut of some kind (appears to be 1/4-20) and I'm wondering exactly what it should look like and if it's brass.

DSCN5064.jpg

DSCN5067.jpg

Thanks in advance for any light you can shed on this.

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