I would guess that hydraulic struts is the way forward, but you'll have to get the right ones otherwise it might be a waste of money either by making it more difficult to close or not making it light enough for your requirements.
The key shaped bracket looks like it would accomodate one end of a safety stay, to prevent the lid from dropping on you whilst in the open postion. Kind of like a bonnet lift bar on a car.
Looks Slow but is Fast
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