I found someone selling a hearthstone III. they say it was built in 1994 or so. it is soapstone stove. to what new hearthstone model does it most closely compare? the mansfield? the phoenix? the heritage? is it as efficient as the new stoves? i am currently considering the mansfield for my needs. does the hearthstone III pale in comparison to the effiecency and heating capability of the hearthstone mansfield? any info on the heathstone III is greatly appreciated. thanks.