All four have now been issued on Blu-ray since Saigon was released this year. The films are:
This Gun for Hire (1942) is based on a Graham Greene novel.
The Glass Key (1942) is based on a Dashiell Hammett novel
The Blue Dahlia (1946) has a script by Raymond Chandler
Saigon (1948)
They are all worth seeing. I would classify them all as crime films with This Gun for Hire as the best and Saigon (with a very unfocused plot) as the weakest.
This Gun for Hire, The Glass Key, and The Blue Dahlia are currently on DVD as part of a collection: Film Noir 10-Movie Spotlight Collection
The first three are on Blu-ray from Shout Factory; Saigon is on Blu-ray ffrom Kino Lorber
I just watched China (1943) which stars Ladd and Loretta Young. It’s worth seeing.
Sad! 