Pat scallops thoroughly with a paper towel to remove excess moisture and ensure a good sear. Combine seafood seasoning, salt, and pepper; sprinkle on both sides of scallops.

Melt butter with oil in a large skillet over medium-high heat. Add scallops, being careful not to crowd skillet; cook until golden brown and a crust starts to form, about 3 minutes per side. Cook in batches, if necessary, to avoid steaming the scallops. Be careful not to overcook. Transfer to a plate; cover to keep warm.

Add wine, vinegar, and mustard to skillet; cook over medium heat, stirring constantly to scrape up browned bits from bottom of skillet, until glaze slightly thick and syrupy, 3 to 4 minutes.

Drizzle scallops with glaze; garnish with tarragon.