Something about serials to keep in mind is that Columbia had been officially re-releasing them up to about 1963-1964 at least. They were not played in many theatres, but after Blazing the Overland Trail they did re-release about two older titles per year. I am working on a listing of all of those re-releases.

On top of the re-releases, there may have been additional titles that you could order from Columbia. I was told that even today there are a few serials you can get from them if you want for your theatre. They are not being offically re-released, but are available if you order them.