Well Dan.....I'm not personally all that familiar with the Astra 400. Neither the Blue Book or the Standard Catalog of Military Firearms makes any mention of the 400 either having (or not
having) a manual safety....other than the grip safety.
The 400 was produced from 1921 to 1945....a period of 34 years. It's possible that some time during the production run, a manual safety was added.
Here's another possibility....the Blue Book states: "This particular model in reworked configuration has recently been imported in large quantities".....it's possible that "reworked configuration" was the addition of a manual safety by the importer in order to be able to import these guns for sale in this country.
And further......take a look at this pic:
This exploded view seems to show three
#38 Grip Safety.....OK this one I understand
#10 Safety Catch....is this a manual safety, or does it merely function as a slide "hold open"?
#29 Magazine Safety....manual safety? Or does it simply prevent the firing of the pistol with no magazine inserted?
I dunno......your guess is as good as mine.....