Huben Huma Reg for Huben GK1

Looking to remove the Huma inset gauge from the bottle end cap on a GK1 reg. Just got my reg in and after installing it I have a leak coming from the gauge. Already emailed Huma but figured I might as well figure out how to remove them for future reference. Anyone know what specialty tools you need, or how it’s done?
 
To clarify you’re saying this black piece coming out is the cover?

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