The insert in the second photo is from Alpha Watch. It is a chrome-plated brass reproduction of the Rolex Yachtmaster insert and fits the 6309, et. al. rotating ring nicely but needs to be centered and cemented in place with heavy-duty epoxy. The chrome is very thin and extreme care must be used when working with the piece to avoid damage.

In the fourth photo, it not an insert but a whole rotating ring made in stainless steel and came with the watch. This rotating ring does not interchange with other watch cases.

I hope this is helpful.