JL's only line that exists today with a 15" in it is the W3. back in the day they had a 15W5 and 15" and 18" models of the W6. it is probably an old one. anything can power that sub other than a JL audio amp. i believe that sub is dual 6 ohm, so you are looking at a 3 ohm load.
I think that sub is 400watts continuous, so maybe a jbl 600.1 would be nice with it and wouldn cost to much. With a 3 ohm load it would output around 450, just set the gains correctly so you dont overload it.