BoxRec

At last, footage emerges! God knows where the original film is now, but thankfully a portion of it was included in this 1975 broadcast.

(The linked channel is worth following on YouTube btw, he has good fights often in great quality.)

03.07:

Good find.
That was a crossroads fight. For Mathis, it pretty much ended his career.
For Lyle, it was his first big win. He was a dangerous fighter.

One of the more fearsome punchers we've seen.