The first Coker unicycle I saw was at the 1998 USA Convention (July). It arrived along with David Coker and was available for all to try out. Then it was raffled off at the end of the convention to Gilby, who started a tradition of winning Cokers in raffles. 
But I think it still took several months before Cokers were available for people to buy. I was skeptical, as the cycle was made from basic Taiwan unicycle parts (other than rim, tire and spokes), so it seemed pretty weak. Also I didn’t like the way it rode, because I was used to a big wheel with solid rubber tire. Those tires have very low friction, and can turn on a dime and do spins easily. The Coker only wanted to go straight, even after I added a lot of air into the tire.
It took me until 2001, when I borrowed one to race in the 10k, for me to appreciate that going straight is not a bad thing. That race was over very quickly for me, and I really enjoyed the ride.
As of 1998 I had heard of Coker Tire before, but only from the car side. But it didn’t take them long to gain a reputation once they got into the hands of unicyclists. Despite what many of us thought, those narrow wheels with their flimsy rims held up to all sorts of abuse, both on-road and off. Before Coker unicycles, long distance riding was a rare thing, done only by the hardiest of unicycling souls!