Effects>Color Correction>Black and White
Then to really class it up add a black solid to the comp, double-click the rectangle tool to add a mask to the whole thing, set the mask expansion to about -40 pixels for HD video, then mask feather to about 100 pixels and invert the mask to put a black round cornered vignette on the footage. You could also experiment with some of the Image Special Effects like Light Leaks Layer markers which can put a light leak over the shot where ever you put a layer marker.
Ortho Chromatic film, the only movie film they had in the 1920's was almost completely insensitive to red so you will need to monkey with the settings in the Black and White filter by boosting red and maybe cutting down some blue.
