Here’s how to how to solve the alchemy cabinet puzzle in Nancy Drew: Mystery of the Seven Keys.
Once you solve the alchemy black stone puzzle and get the ingot with the three symbols, take it to the cabinet just around the alchemy table. The cabinet is locked with a three dial mechanism. The goal is to match the three symbols on the ingot with the viewfinder space on the cabinet.
Start with the innermost (smallest) ring. Click within the rectangle viewfinder and drag your cursor left or right to rotate the dial to get the “essence” symbol, which looks like an upside-down V with four lines horizontally crossing it.
Next, rotate the center dial to align with the “steel” symbol, which looks like an open 4 but with an extra vertical staff.
Lastly, rotate the largest, outside dial to align the “phosphorous” symbol, which looks like a triangle on a staff, and the staff has two small horizontal lines on it. The door unlocks and opens.
There are only a few things to examine and collect in here. The space with the colored gems contains a paper of an hourglass, and under the blue gem is a coin you can pick up. This coin is the only one you can keep because it has the symbol for “copper” on the tail side. There is a drawer in the upper center are of the cabinet, next to the beaker. This drawer has an important book you can collect, and underneath is an old paper with a sketch of some gears and the astronomical clock. You can also look at the sextant (navigational instrument) in the lower right, but there is no purpose to it.
Here’s the full video walkthrough:
