I picked up a 5C collet fixture at the last auction I went to that was missing the collet retention plug. Does anyone here have this same style of 5C collet fixture? And if so would you be willing to shoot a picture of the retention device.

I have similar fixtures so I could cobble something that would work up but there are two threaded holes in the bottom that I am not sure what their purpose is,

Here is another view of the side,

Any help would be appreciated,