It's the cover from the Fuze Eliminator, which came out shortly before the Inferno line and Activator were introduced, so I'd go with PK18 like the rest of the Brunswick particle balls. The Ambush used the same cover, but a pearlized version rather than a solid/pearl hybrid like the Sidewinder.
The only BVP ball with an Activator-based cover is the Mammoth.
SH