Question Mysterious 1987 Catlina 3AL S80

[Rudygates]

I recently got a tank that from the markings is a 3AL Catalina S80 born in August of 1987. On the inside of the tank it looks like a nipple Like what is left over from machining). This goes against everything I know about how AL tanks are made. (There is also some brown staining in the bottom that looks like rust, but it's and AL tank??)

Any ideas on what could be going on with this tank? Did Catalina ever use a press with this ridge on the bottom?

Thanks!!

 

[rjack321]

Its normal and a relic of the starting slug of aluminum in the extrusion press. Maybe 2-5% of tanks have extrusion artifacts like this

 

[bletso]

Nothing to worry about and as it's a Catalina it will not be made of the 6351 material.