Heiser made some spectacularly large and heavy tanks for Beuchat in the '90's, most notably a 220 bar 140 and a 300 bar 190. Both measured approximatly 8" x 30", and weighed 63 and 87 lbs respectively. They were supposedly made using the pierced ingot or tube formed process usually used for industrial tanks rather than the deep drawing used by Worthington and PST for steel scuba tanks, hence the extreme weight.
They were not a sucess due mainly to the weight and difficulty getting fills, and are no longer in production. Some specs on them are available on the TDI website, but more info than that is hard to find - I have contacted Heiser, Beuchat, and some former Beuchat USA employees trying to find out more, without much luck.
If you or anyone else reading this has one of these tanks, I would appreciate it if you could PM me or post the markings on it.