I have a second gen OM and all my NATOs fit without issue, but I never put a leather band on it. However, on my Neo Monster, I wanted a yellowdog watchband on it and when I got it, the band came with curved spring bars. A novel idea for the yellowdog leather watchbands because they are THICK. I had to use a springbar tool to work the band in. Of course, I had to guesstimate the NATO to ensure I got a good fit.
18, 20, 22, 24mm Curved Spring Bars Double Shoulder 1.78mm Dia. (pack of 20 piec