A specially designed quick coupler is representatively used to removably attach an excavation bucket to the outer boom end of an excavator. A top portion of the quick coupler is pinned to the outer boom end and has a bottom portion with spaced apart recesses configured to releasably receive portions of stick and curl pins on the bucket. An arcuate latch hook is translationally drivable by a hydraulic cylinder assembly toward one of the implement pins to releasably lock it in its associated coupler recess in a manner also captively retaining the other implement pin in its associated coupler recess. Stop structures oppose the latch hook and, using a simple shim arrangement, may be translationally shifted toward and away therefrom to easily adjust the coupler for wear and/or changes in the implement pin spacing. A redundant safety system is incorporated in the coupler and serves to hold the latch hook in its locking position. The safety system includes hydraulic and mechanical locking mechanisms and a spring structure resiliently biasing the latch hook toward its locking position.