GrovTec Shotgun Locking Swivel Set, Fits Mossberg 500, Locking 1 Swivels GTSW31 GrovTec's inception starts when Bob Grover started working for Michaels of Oregon in 1987. He began working for Michaels in the recoil pad/scope cover department and then moved on to the Machine Shop. He held the roles of Black Oxide Finisher" Machine Operator" Machine setup person" Davenport Lead" Machine Shop Foreman" Manufacturing Supervisor" ISO Coordinator and Manufacturing Manager.