Although to many, especially those with perhaps less emphasis on civil aviation, the presence of winglets on these 737s may not be considered ‘weird’ at all, considering how the vast majority of 737s nowadays come equipped with them. However, it must be noted that only the 737 NG and 737 MAX have factory winglets, and these photos are examples of the 737 Classic, which was not offered with winglets. The vast majority of Classic builds had no winglets, and these are some of the ultra rare versions which were retrofitted to include them, likely having only existed in very low numbers, perhaps the low tens. There seems to be at least two designs - the first being perhaps slightly more common and based on the blended wingtip of the NG series, and the second appearing to be a very original retrofit, with a vague resemblance to that of the MD-11.