Is this original 515b cone?

[ALTECMANIAC]

So when you say it was the last repair reference, it means it was repaired by Altec the company itself years ago?

Not necessarily, it was possible to buy the recone kit, and repair your loudspeakers yourself...But 1803035-400 is the good reference.
Ask for more pics to see if the paint is damaged, the dust cap glue is well put...
There's no doubt, this 515-B has been reconed but if the repair was well done, no problem.
For your information, last year, I've repaired my 515 (first serie) and my 416-8B with GPA recone kits (035400) and they works and sound good!
Stéphane M.