The G757-5030 shares a lot in common with the G757-5040 — everything in fact except some subtle colouring and the name; this is the SILVERWAVE version, the 5040 is the SPORTS 100.
Silverwave is believed to be the name Seiko applied to their Japanese domestic market watch models (with water resistance) while Sports 100 was the international version — much like the way early Casio G-Shock watches were branded 20-Bar for the domestic versions and 200m for international (and Foxfire vs Illuminator on later models). They seem to only be naming conventions though and the modules are interchangeable and cases virtually identical.
Like the 5040, the 5030 has two waves on the caseback, indicating somewhere between 10 and 20 bars of water resistance.
The watch feels solid on the wrist, without being overly heavy or bulky (the G757-5000 and G757-5020 do feel more cumbersome).
Feature-wise it’s well-packed, with 12/24 hour time (selectable with the top right button in normal time mode) day/date (where the user has the option of seeing seconds or the date in normal time mode settable with the lower right button), countdown timer, alarm and hourly chime, dual time (viewable as analog, while normal time is still displayed), and a 10/100 stopwatch. There’s also a test function where all segments are displayed and the alarm beeps to check everything is working correctly.
A highly-collectable watch (any of the G757 models are) with a connection to the James Bond film Octopussy (it was the G757-5020 that was used in that film, along with the Seiko T001-5019 television watch).
The module draws a lot of power so it’s advisable to run a good quality battery (Renata preferably, since they have a working voltage from new closer to 1.6v than 1.5v). It takes a single 381/391 battery which should be changed if the display starts to dim or starts flashing.
If the battery is left to go flat in your G757 there is a very good chance that the watch will be dead even after you replace the battery. This module is notorious for dying unexpectedly if a dead battery is left in it. A great shame since it’s by far one of the best digital watches Seiko ever produced and is still insanely popular.
Expect to pay big dollars for one in good condition with a working module — it’s worth the money though.