Sorry scubafanatic, you assume incorrectly.
The picture shows the twins are made of 6498 and appear to have been made in 1979. So the twins at least are made of the suspect alloy which is has the DOT safety notice on it due to potential cracking problem.
Can't make enough of the other two tanks stamps to comment on them.
http://www.scubabomb.freeservers.com/List.htm
The picture shows the twins are made of 6498 and appear to have been made in 1979. So the twins at least are made of the suspect alloy which is has the DOT safety notice on it due to potential cracking problem.
Can't make enough of the other two tanks stamps to comment on them.
http://www.scubabomb.freeservers.com/List.htm