Related Clues:

• "Works for me!"
• 'Super cool!'
• "Super-duper!"
• ''That's great!''
• In the 50s or 60s, say
• Cool, in the '50s
• 'Very nice!'
• On an even keel
• ''Nifty!''
• 'Peachy keen!'
• "Swell"
• Warmer than chilly
• Calm under pressure
• Hard to rattle
• 'Way cool, man!'