Here is Good Ole Dog's (aka SkunkVA) pic of Chem 91. Recognized as the Chemdog that started it all. The one Chemdog gave to SkunkVA, and later got back from him.
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^^^ page 11 of the 91'chemdog thread on Ic mag
^^^ page 125 of that same thread. ISP's Chem 91 grown by Hammerhead, 40 days into flowering.
IMHO Chem 91 is more potent than Chem D. ISP's version, because it has preinvasion afghan in it, has a better flavor and slightly heavier trich coverage than the SkunkVA cut. The consensus on Ic mag of the majority of older growers is ISP's version is closer to the real Chem 91 (SkunkVA) than the JB's cut that often gets passed around as Chem 91. I say until you grow it and try it for yourself, you're missing out. I've grown all of ISP's Chems now, and none have disappointed. In fact, their IC91(Insane Chem 91) is too potent for me, it totally wrecks my day, so I don't hit it often or mix it with lesser strains when I do.