Both the Achilles floors and Harmon floors were laced, and again, the only way to tell is by looking close at, and feeling, the floor material. If it feels smooth and slightly shiny like the tubes, this is rotocured material and it would be an Achilles floor. If it is very dull grey with a more velvety finish, then it is probably one of Tracey's floors made of Reeves hypalon or gray neoprene. My guess, looking at the color of it and knowing that no I-beams have blown (there are no big long patches on the floor, right?), it is most likely a Harmon floor.
Way back in the early 80's, the lifespan of Achilles outfitter grade boats was as good as you could get, and despite claims to the contrary, Avons were not superior other than having lower weight. Later in the 1980s the super heavy outfitter Achilles disappeared, but even then they remained very good. I would argue that Hyside's material had a slightly harder finish with better abrasion resistance, and it was stiffer inflated which is good, and they certainly made better floors by far than Achilles, but this Achilles is still a great raft if not the best handling one. For class III and moderate class IV I think it will be just fine.
I know you don't want to barter with a buddy, but I do think it would be fair to offer a bit less considering the age & all.