Originally Posted by
noglider
Grim, mang-alloy is manganese molybdenum carbon steel, which is what Reynolds 531 is made of. As far as I know, it's functionally equivalent to chro-moly. It's about the same strength, so you can make it thin walled for lightness. I don't know if Tsunoda (the maker of Lotus) made it thin-walled, though.
Thanks for setting me straight. I just weighed my 63cm Prestige and as a single speed stripped of its shifters and deruiailers it is weighing it at 22ish lbs. My Raleigh (that may actually be a Holdsworth) has a 27.2 seat post and I know that the Lotus runs a 26 something post so you are correct that on at least the prestige it is not a thin wall.