Are they negatives or positives? The last one on the right looks to be a positive -- the others are too dark to tell one way or the other. if they are positives, then they might have been created for a slide show (magic lantern sort of thing). And if that is the case, then we are one step away from the camera that made the original images, which makes it difficult to tell much about the camera (other than there may not have been neither enlargement nor reduction done in image size).
Who knows? Maybe we are looking at the first family slide show!