Most if not all the coils have that rust……..as long as the plastic case isn't cracked and the coil functions, it is still good. Clean off the rust with a wire wheel or dip the ends in evapo rust or metal rescue, if you need it to look good again.
Back in the good old days when my bike and I were much younger and you could still buy parts from Honda I needed a left coil. They said 80 dollars and I thought no way. I found an old gm car coil, liquid filled of course, laying on the ground behind the garage I dealt with. I grounded the negative side with a wire and pt the wire from the Cdi on the positive side. Fired the bike up problem solve just enough room under tank for one. Sold the bike a year later and got it back last spring. Rt side not firing right. Off with the tank and there is the GM coil still firing properly after almost 20 years. With a gl or non cdi set up this would not have worked so well. The main thing replacing the coils is not if they are honda but that you have the right resistance in the primary winding and thus the right number of wire coils. I replaced both coils last year with ATV coils from a Kawasaki and all is well.
Thanks, guys! I did some research and, yep; rust is pretty much par for the course. And the only way to test coils is to see if they bike runs with those coils. Should be able to "test" these coils some time this week, if all goes well. Woo!