I have a pair of 100% leather
Mittens with gauntlets that were made by
Olympia Sports Co. They're sheepskin lined..no heat. I've had them for as long as I can remember (40+ years..?) and they worked well for iceboating down to -15 F @ 60+ MPH under sail. I also used them motorcycle riding in the winter down to about 15-20 F for hours on end.
NB
http://www.olympiagloves.com/