when looking to the negatives made with my three minoxes, each film has a signature of the camera: exposed with the A (III S), the negatives are rectangular with straight borders. But with the LX, on one short side of the negative, there is a convexity of about 1 mm in the middle of the border line. And with the BL, this convexity is at the beginning of the short side. Does anybody know something about this signes? Are they typical for each model? So which signes do the B, the C, and so on expose onto the film? <p> Or is this just due to the different production years? <p> Either Hubert Heckmann nor the german instruction manuals give any hint to this "fingerprint" of the different models.