Need Help Reading CO2 Cylinder

[ldgenius2000]

Just got a CO2 cylinder and need help reading the markings on the cylinder.
First Line: DOT3AA2015 SPUN
Second Line:SPW-816700C 9 symbol (like a C and L) 80+ star ()
Third Line: OT11

Got this tank on ebay trying to figure out more about it and would appreciate any help you all can provide.
Thanks.

 

[elmetal]

DOT Means the department of transportation has approved.
3aa means standard steel
2015 is service pressure in psi

I think the second line with spw and whatever is the serial number plus manufacturer

OT seems like a manufacturer mark and 11 could be many things, year manufactured (it's def not.), tare weight (quite possible), tank capacity (possible) or month of manufacture.

 

[elmetal]

I apologize. OT could be the mark of the inspector and SPUN is manufacturer.

 

[ldgenius2000]

Yeah I'm trying to figure out when it needs to be hydrotested

 

[elmetal]

it should be stamped elsewhere. not one of the three lines.