I'm not sure how one would rate the film, but that camera actually has a variable aperture (3 choices) and a bulb type setting for longer exposures.

There are two tabs located on the top of the camera to change these settings.

Looking down on the camera top as if you were going to compose a scene through the viewfinder, the left-most tab is the on/off toggle for the shutter's time exposure setting. Pull the tab up and the shutter will open when the shutter release lever is moved downward. It will close when the shutter release lever is returned to its original position.

To change the aperture, pull the wide tab located midway between the time-exposure tab and the viewfinder window.

There are three settings, the smallest of which is selected when the tab is fully extended. There is a crude detent midway that lets you know when the tab is in the proper position to line up the aperture and the lens opening.

To get a feel for where they are located, you can shift the shutter lever tab to its time-exposure setting (extended) and open the shutter (please, no film in the camera yet!) and see for yourself the different sized apertures that are selected as you pull out the aperture tab. Feel for that midpoint detent as you slide the tab in and out. Otherwise, fully extended is the smallest aperture and flush with the camera top is the widest aperture.