Questions about metal oxide recitifers

[Algojervia]

Hi
Recently got a few bags of assorted electronics and in them I found what I believe is a bunch of metal oxide rectifier. Using the diode tester I measured a drop of three volts over the outer and center plate. So I have some questions since I never seen this type before.
First of all, are those the selenium or copper oxide type. If they are the selenium kind, how dangerous are they, I want to dismantle one just to have a look but I though I ought to wait until I heard what you have to say about it. As far as I understand there is only some risk if I would somehow vaporize the selenium.
Secondly, could I have any use for them in some fun experiment or so? They seem to be enable to carry some current unless they are just inherently inefficient.
And last, the person owning this before me was obviously a car audiophile (among all the other stuff I found over ten 400v 2.200µF caps) so what was his intended use for the rectifiers? Did he build his own rectifier circuits for the alternator or are there any other uses in car audio?

[SeanB]

Don't think those are selenium, they never had a shiny anodised aluminium plate, more a lot of steel plates for cooling with a paint on them.

mor clearer pictures of the sides and all angles will help, that might be a split charge controller for a car, or some other device.  In any case 400V 2200uF capacitors are more commonly used in high power inverters, a 2200uF capacitor in a car is typically only rated for 25V, and is quite small. Those 400V ones will be as large as your hand each, with screw terminals on the top.