I don't think I gained anything by taking out the cover glass from in front of the lens on the JEM box camera. Film choice, processing and ambient lighting all seem to have more of an impact. Rather than continuing to beat a dead horse, I think I'll just pass along what I've learned recently about the JEM JR. 120 for anyone else who might want to take up the cudgel.
The first thing you notice in the above photo will likely be the rather panoramic appearance; the camera has overly large frame rails which cut into the width of the 6x9 image quite a bit. However, it is important to note that properly loading the film requires the leader to be placed against the back of the frame rails rather than threading it through the slots under the rails. I tried that and got more area covered on the film, but that places the film plane about 2mm too close to the lens and cuts down sharpness.
Film unloading also requires some attention from the JEM user. The film advance requires turning the key in a counter-clockwise direction. That means that the film is wound onto the take-up reel against the curl of the film and backing. When you go to take the film out of the camera you will find that it wants to spring outward, unwinding from the reel in the process. So, one is well advised to remove the film from the camera inside a dark bag.
Other than film handling, the JEM is pretty much a standard, low-end box camera. The slow shutter speed demands a steady hold, preferably braced against something solid. The lens obviously has a tendency to flare, so flat lighting of the subject is likely to yield more pleasing results. With the addition of some red or yellow filtering it would be possible to use a wider latitude film like tri-x or tmax 400 which would help to keep the highlights under control.
Another possibility of filtering is that it might compensate to some extent for chromatic aberration -- that is, different wavelengths of light focusing in front or behind the film plane. Not all simple lenses are made alike. Better quality ones had additives to combat aberrations and some even sandwiched two types of glass. I'll give filtering a try next time I get some film in the JEM JR.