When was the first mechanical broadhead patented? Or, when was the first one marketed?

[nigins]

When was the first mechanical broadhead patented? Or, when was the first one marketed?

[HawgNSons.Com]

Barrie Archery?

[Buckshott00]

Invented, patented, and marketed are probably different thing in this case. Archers had been experimenting with mechanical broadheads all the way back into the 1950s.
Rocket arrow heads are probably the first ones to make it into mass market back in the late 80's but there are known expanding heads all the way back to 1956 if not earlier.