In education in optics the explanation and demonstration of aberrations are an essential part. Of the third order monochromatic aberrations usually most attention is paid to spherical aberration, astigmatism, field curvature and distortion. Coma is more complex to explain and more difficult to demonstrate in its pure form. In 1933 Van Heel has designed a 'lens with pure coma' for demonstration purposes. With this lens a number of photographs have been made to show the development of the coma circle from the pupil plane (single circle) to the image plane (double circle) and to demonstrate the coma images around the focal plane. In 1948 a second lens for demonstration of coma was made by Van Heel. Both lenses are described in this paper and their performance is determined by computer calculations. Comparison with original coma photographs is made.