Thanks for weighing in, Bill.
On the lower end I took off the big nut, the tanged washer under it, the spring, and the two washers under the spring. I was left with nothing but the 3" long threaded post that has flats on two sides.
The upper end just has the long-ish pin. The vent glass/frame slides about 1/4" up and down, but not enough for the upper pin to move down through a hole before something (?) on the bottom end stops its downward movement. I thought it was the frame bottom that the 3" long threaded post goes through.
Hopes this makes sense.
Bill