This ref 2577 measures 34mm in diameter and houses a cal 354 “Bumper” automatic movement. These were the first automatic movements introduced by Omega and instead of a full rotor employed a pendulum weight to wind the watch. The pendulum did not fully rotate and when it reached the end of its movement it would hit a spring, creating a little bump. This “bumping” sensation has given the watch its “Bumper” moniker. These watches came with a wide variety of dial and the example in the picture is quite unique, as it has an original two-tone, cross hair, waffle textured dial. Many of these dials were refinished throughout their service history, so finding an original example is somewhat of a challenge.