When I asked questions regarding identifying early Zaskars on here a couple of months ago, the consensus was that the 6061 is not necessarily going to be there, even on a pukka Zaskar. However - the frame number on any GT frame made in the Taiwan (i.e. Pantera that we might suspect in this case) begins with a letter not month/year numerals. Frames made in Huntington Beach, California have frame numbers beginning with month/year numerals.
My Zaskar has no 6061 stamp, and the frame number starts 0491 - which bears that ^^ out.
edit: The frame you're interested in looks totally identical to mine, so I'd say it's definitely a Zaskar.
Cheers for that extra bit of information mate,i'll keep that in mind tommorrow when i have a look. What year is yours mate? And anyone know when they changed from u brake to cantilevers that would narrower the year of the bike down a bit.
Marin:1988 Pine Mountain
Konas:1989 Explosif,Fire Mountain
Muddy Fox: 1990 Pathfinder
1992: Dave Yates Diablo
Denton Cycles: 1995