How do I test for a bad distributor?

Just like the title says. I believe my rough idle may be, in part, caused by a bad distributor. Timing is a little funny, but not really that bad. With the EST wire unplugged it slowly retards from 6* BTDC at idle to about 5* BTDC as I increase throttle. Then it hits a certain RPM where it advances suddenly to 12*. Could this be causing my rough idle? Is the "inductive pickup" located inside this distributor or is it external? There does seem to be too much movement in the distributor but without a good one to check against it is difficult to tell. What should I look for?

Here's some pics:

http://www.geocities.com/casenjoe/100_0785.jpg
http://www.geocities.com/casenjoe/100_0786.jpg

Pretty nasty looking, I know. I didn't realize the pictures would be so big but at least there is plenty of detail.

Preliminary tests: When try to move the shaft up and down there definately is about 1mm of play there. Side to side it seems pretty stable. The bronze-ish circular piece thats right under the rotor on the outside can rotate about 10* with minimal force. As I rotate the gear I seem to feel a slight resistance every quarter turn. I don't know what thats about or if its normal.

Preliminary tests: When try to move the shaft up and down there definately is about 1mm of play there. Side to side it seems pretty stable. The bronze-ish circular piece thats right under the rotor on the outside can rotate about 10* with minimal force. As I rotate the gear I seem to feel a slight resistance every quarter turn. I don't know what thats about or if its normal.

the up and down movement is normal, and the resistance you are feeling when you turn the shaft is the magnetic drag being caused by the reluctor and trigger wheel. Thats also normal. That ignition control module on the distributor looks pretty old, have you tried having it tested at autozone? they test em for free i believe. Your problem probably isn't the control module though. When they go bad it's either they start, or they don't, but thats just my experience. I imagine they could go bad slowly and maybe cause a miss. I would suggest buying a COMPLETE KNOWN GOOD USED distributor from the classifieds section. Saves you alot of money and will eliminate the problem, or eliminate the possiblility of a bad distributor. You say you get no check engine light right??

to check output you need a graphing multimeter,
a Snap-On Vantage tells you how to do it and what it sholud look like
if you can get a hold of 1 its easy to do

IS THAT SAND!all over it ?? Not trying to be an @$$, but that is what it looks like. If it is it could be a possibility that some got inside the dizzy.

Corrosion I believe. The distributor is on my list of stuff to replace, but I want to find the actual source of my rough idle first. Right now the timing is pretty consistant at idle and I don't know of anything else the distributor could do to cause a rough idle.