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.
Rob
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Genetic pollution damages wild
stocks, bonk those Hatchery Zombies!