I've seen a tale of the tape and it said Tyson's arms were 16 inches in circumference. In my view this just cannot be - he had at least 17.5''. Wlad Klitschko has about 18 inches, Tony Thompson 16 (according to German television).
He appeared to bulk up a lot later on. He was at his best when younger, visibly smaller, but a lot quicker.
Yes, he gained about 20 pounds over the years. But still, I've never seen Tyson with only 16 inch arms I don't think.
I think they were close to 25 inches in circumference, an attribute that helped him become the only man to ever punch a hole straight through a solid marble column. I still can't believe he decided to do it bare-knuckled.
Remember that I'm talking about prime Tyson here and I'm not surprised if you haven't seen him, very few have, although there have been some reported sightings in the middle of '88. The Tyson you and many others are thinking of probably had around 16,5" biceps and a tendency to malfunction when faced with adversity.
I'm sure you grew up with young Tyson, as I also did, but Prime Tyson is something completely different, he appeared for a millisecond during the Spinks fight and was never seen again. Blink and you missed him. Young Tyson probably had between 16" and 17" inch biceps no doubt.