The Dodgers and Mariners have a substantial trade history, as Andrew Friedman and Jerry Dipoto have made a couple of trades in recent years.
The most famous (or infamous, from Seattle’s perspective) is the Zach Lee-for-Chris Taylor deal in 2016. It was a straight 1-for-1, with both teams giving up on former top prospects. It looked like a decent gamble for the Mariners, but Lee didn’t pan out while we know what happened with Taylor.
The other notable deal was a bit more minor, as the Dodgers acquired infielder Drew Jackson and right-handed reliever Aneurys Zabala for Chase De Jong.