I recently aquired a new  Russian 75 round drum mag.  I have never owned any AK drums before so I'm not sure about this small knob on the back let alone anything else about this drum.  This knob is not attached to the drum, looks like it would be a mini removable wineder tool. Any input?

the knob you speak of is the take down knob. to use it take a flat head screw driver and depress the bar in the ceter of the knob. turn counter clockwise and then you will feel the knob "break" free. simply lift up and it will come off. now you can pull the back cover off of the drum and get all the cosmoline out of it if it came new in wrap if not you shouldnt have to worry about breaking it down. WARNING do not take out the dummy round and let spring unwind! if you do remove the dummy rounds put somthing in their place to hold spring tension. (DO NOT USE FINGER) clean the dummy rounds and replace asap.  

hope this helps