Warren_L:
I am not familiar with the Walter Kidde tanks, but I thought the manufacturer was stamped into the top of the tank near the neck, is it not?
Easy, If is says CATALINA, it is not of the suspect alloy. If not it is. Of course it is more complicated than that. But Catalina never used the suspect alloy, almost everyone else did including Walter Kiddie.
At the top of the tank the alloy is stamped as E**** where the * is DOT exemption number.
The below is not an all inclusive list. Check DOT website yourself. You can search on the alloy numbers from your tank.
All DOT-3AL tanks manufactured under one of the following exemptions or special permits: 6498, 7042, 8107, 8364, 8422
All composite cylinders manufactured under one of the following exemptions: 7235, 8023, 8115
All Walter Kidde DOT-3AL scuba tanks.
All Cliff Impact DOT-3AL scuba tanks made before July 1990.
All Luxfer 80.8 cu. ft. scuba tanks (S80.8) made before May 1987.
All Luxfer 72 and 100 cu. ft. scuba tanks (S72, S100) made before August 1987.
All Luxfer 80 cu. ft. scuba tanks (S80) made before January 1988.
All Luxfer 50 and 92 cu. ft. scuba tanks (S50, S92) made before April 1988.
All Luxfer 30 and 63 cu. ft scuba tanks (S30, S63) made before May 1988.
All Luxfer 40 cu. ft. scuba tanks (S40) made before June 1988.
All other scuba tanks made in the US before February 1990 (except Catalina).
All scuba tanks not made in the US.
Unless proven otherwise, all scuba tanks in the above list should be assumed as being made using the 6351-T6 alloy.