Yep, it's an aluminum wound string. Pretty smooth, hardly any squeak and works well on a concert scale as well (using it on my BP M-Style concert currently).
I bought a "Thomastik-Infeld CF27 - 3rd string (g) .027 chrome steel flat wound" from Strings by Mail and that worked well as a wound 3rd. Very smooth, very soundless like the Fremont Soloist.