21st Special Operations Squadron (21st SOS)
When the 21st SOS stood up in 1988 they initially looked to keep the old Jolly Green Giant patch.
There are examples which feature the JGG with 21st SOS titling across the top.
The squadron decided to go with their Vietnam heritage and the Dust Devil design returned to their patches and later Taz, the Tasmanian Devil.
When flying in SE Asia the 21st used the Knife call sign. They participated in Eagle Pull, Frequent Wind etc. During the Koh Tang Island/SS Mayaguez rescue attempt one particular 21st machine was famed for the number of rescue attempts it made under withering enemy fire - Knife 51 flown by Richard Brims.
When the 21st SOS stood down at Mildenhall in 2007 their farewell flight was lead by MH-53M bearing the same historic call sign Knife 51.
Prior to the arrival of the 7th SOS's Osprey's there was much speculation it would be the 21st that would stand up to fly them. That wasn't to be but they continue to fly with the Knife call sign and feature a healthy number of ex Pave Low crew members amongst their number so the heritage lives on.