Odd design: It doesn;t look like the ammeter is hooked up to me. Assuming 120 VAC and you don't have one in front of you.
top bottom, left right,
DC ammeter (does't look like it's hooked up)
red/blk binding posts
Fuseblock and holder
Power resistors and bracket
Capacitor and clamp: probably 5000 uF at 400 VDC or therabouts.
An industrial switch with at least one contact block (The green thing)
A full wave bridge rectifier (probably 400 to 600 PRV at 25 Amps) mounted on a heat sink. A light film of silicone grease is used to improve thermal contact;
Terminal block - behind the capacitor
Voltmeter
Variac
Comments:
The green things are wire wound resistors, probably 200 W or so. My guess is the design allows two current limiting resistors. The right lugs can be swapped. One of the resistors essentially does nothing.
An ammeter is usually a micro-ammeter that is made to measure amps by converting it to read voltage across a shunt (typically (50-100 mV max) with a resistor. They can read directly.
Aside:
Some of the ebay digital meters put the shunt in the ground connection. That's probably not a good idea.
it's close to this:
http://mrtitanium.com/anodizer.html
The green switch might select the two current limiting resistors rather than being power.
WHAT I DON'T LIKE ABOUT THIS DESIGN.
1. everything is open.
2. There is no isolation: i.e a 120:120 Isolation transformer.
For some reason the plating industry likes to call these things rectifiers.