Pans were often cut from different directions with a graver to raise a
tooth then gold sheet was driven onto the teeth to lock it in place. Just like in making gold inlays. But care must be taken to assure the "teeth" are not exposed in the process.
Gold vent liners were, if I am proplerly informed, peaned into an iron liner with a large hole that was counter sunk on both sides or perhaps like the drawing on the left.
This is why, I think, even double guns had threaded holes into the opposite side of the breech. But I can't find any writing from the past that describes the installation of vents. So there is supposition on my part.
Gold was used for vents in high grade guns in England/Europe until a process was developed to make Platinum malleable then Platinum was common.
I suppose that some grades of gold may be hard enough to thread and screw in.
Someone here has to know more than I do on the Gold vent liner topic.
Dan