HCH is the taper designation. The rod you have was made on the cusp of lines going from tapered silk to modern synthetic lines. If I were you, I would try taking this rod to a shop and try casting it with a 5, 6 and 7 weight lines, seeing which one works best. I would be you prefer the 5.
You can fish a 5 for summer steelhead without any problems. I took a summer steelie on a 4 in September. Ideally, I believe that a good rod is somthing between a 4 and a 9 here, with the ideal crossover at a 7. So buying an 8 is not out of the question, but you might have more fun just fishing your 5 for trout, there are more trout than steelhead and you will gain more confidence.
Congratulations on your casting. Keep up the good work.
Genetic pollution damages wild
stocks, bonk those Hatchery Zombies!