Yes, the lower pipe thingy on the caliper is also a dead giveaway - it isnt needed on the later calipers. Have read somewhere that the design is less efficient than the later ones, but I had a go on an old Thundercat years ago & the brakes were impressive.
Someone has swapped over the calipers for some bizarre reason, if it were me if they work fine I could live with them but there are loads of newer ones on ebay if you want to put her back to standard.