I think single coil filaments is less efficient then coiled coil filaments because it run at lower temperature. In any case go to www.lamptech.co.uk and click on the Incandescent lamps section for more information about this.
It less efficient because it loses more heat to the surrounding gas (because of more exposed surface area), so it needs more power to maintain a given temperature and thereby light output.
Nope it's a coiled coil filament. Single coil filaments are the ones with 3 supports in a horizontal C shape. Vince if yours are 500 lumens they may be 1000 hour instead of 1500 hour.
Yes they are 1000 hrs. rated. Same thing for 100W lamps, which are rated at 1470 lm. I have a 4 pack of the 1710 lm Crystal Clear bought several years ago.