Case Tumbler

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The lube-a-matic is for lbing cases that you cast yourself. The green media is most likely the treated Lyman stuff. Depending on how old it is, put 1/2 a dryer sheet in the tumbler with your brass and they'll have less of the greenish finish and be just as clean. Quite the score you got there...

I'm just getting into casting but I believe the alluminum plate is a heater for the lub-a-matic.

I think bmac meant it is for lubing bullets you cast yourself not cases.

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If memory serves correctly, the plate you have is an idea RCBS had a few years back to enable a person to mount the plate onto the bench and then easily attach & remove a variety of presses.  That way your bench top would be clear for other projects.

They still make it.
http://shop.rcbs.com/Products/Accessories-Replacement-Parts/Reloading-Accessories/Accessories/Accessory-Base-Plate-2.aspx