Although impossible to identify exactly, this lens could well be in the neighborhood of f4 as many were in those days. This would enable short exposures with the emulsions of the day. Photographers became adept at fraction of a second exposures as emulsions became faster.
Assuming a film or plate speed of 16, f11 @ 1/10th second would not be too hard to achieve. Of course smaller apertures would provide for longer shutter openings.