D. Gold bases this on work from the 40's that I'm sure was done well, but is what it is and not more. Things are not so black and white; others have said that it is less potent, including some who have also claimed to have made it.
This is from 1945, at the end of the research by this Adams group, where potency is shown as 2X. You can see a table here.
Neither it nor the THC it came from was pure.
This potency is based on the motor coordination of dogs.
If I had some acetic anhydride I could find out for myself, but it's not easy to obtain in the US for most people since it is regulated.
Mechoulam wrote a definitive book in 1973 (Marijuana), which this is from:
Chapter 2 - Structure Activity Relationships
Table V - Activity of delta-1 and delta-6-THC Derivatives and Related Materials.
This table gives the dosage necessary to produce certain observable effects in rhesus monkeys: - indicates no change; +-, tranquility; +, drowsiness,decreased motor activity,occasional partial ptosis,occasional head drop; ++, stupor, ataxia, full ptosis, suppresion of motor activity, typical crouched position ("thinker position") for up to three hours, presence of reaction to external sensorial stimuli; +++, severe stupor and ataxia, full ptosis, immobility, "thinker position" lasting for more than 3 hours and absence of reaction to external stimuli.
Dose (mg/kg) Activity