b-movie

Not a B, just a relatively modestly budgeted picture. Compare it to something that really was a B picture (if one that turned out to be a surprise huge hit) in the same era: 1942's Cat People.

The first thing is the budgets. According to the numbers listed on this site, The Maltese Falcon had almost 3 times the budget of Cat People ($375K to $134K).

Then there are the casts. For the most part the studios kept their A picture actors and B picture actors pretty segregated (at least for the roles big enough to get in the credits). Of course, if you go looking then you can always find exceptions to everything; but as a general rule of thumb, it's valid.

In Cat People, the biggest name in the cast is Simone Simon. It's true that she was a star in her native France, but while she was in the US during the war (aside from a small part as what amounted to "Lust" in The Devil and Daniel Webster) she was stuck in B movies. I've even read / heard stories about her being vetoed from lists of casting suggestions for A movies *because* she had done both of the Cat People movies. The mere fact that she had done multiple B pictures rendered her completely untouchable in the eyes of may A producers of the time. It didn't matter that Cat People had been hugely profitable with her doing a very good job with her role, it was still a B. (I have seen it said that a career could survive being in one B picture, but not two.)

The rest of the cast of Cat People were strictly B players. Not that there weren't some other good actors in there; there were. They were just all people who got stuck on the B side of that divide.

The cast of Falcon was a whole different deal. Of course, it didn't have any of the huge stars of time (Bogart's time on that list hadn't quite started yet), because it didn't have "prestige picture" sort of budget. While Bogart was just starting to get lead roles, all those second banana roles were in A pictures. You're looking at things like Petrified Forest and all of those movies where he got killed by Cagney near the end of the story.

Astor had been playing romantic leads going back to the silents in the 1920s. Even when her career declined some through the 1930s, she was still working on the A side .... sometimes in some pretty significant movies (in terms of the budget & prestige at the time). She was in such things as Wyler's Dodsworth, the Ronald Colman version of The Prisoner of Zenda, and Brigham Young (with Tyrone Power & Linda Darnell).

Now, Lorre is one of the exceptions who was in the process of moving his career from working in B movies to A movies, but his last movie before Falcon was a Clarke Gable / Roz Russell vehicle (so, very much an A picture). However, he would have been a well known name at the time from playing the title character in the Mr. Moto series. Greenstreet had spent his entire career on the stage until Falcon came along; better than the negative associations of have been in B movies.

So ........... Yeah.
I don't see Falcon as having been an actual B picture, at all.

Apart from any considerations of budget this film's running time is far too long to be a B-movie. B-movies were second features or supporting films that were limited to below a 75 minute running time in the 1940s as far as I know.

I can think of one example where a 72 minute film had to be increased by three minutes by shooting an extra sequence for it. This was because they wanted to screen the film as a main feature.