I don't know anything about these, I believe they are "new" old stock and may or may not have rust, wear, scuffs scratches, etc. and the chrome may be dull, all from being improperly stored, therefore listed as used. I have a few available and will ship the nicest ones first......I have pictured the worst ones of the lot, most are not this bad!
Arm is 150mm and wheel has 46 teeth, diameter of wheel is about 190 mm. This does not include the left arm nor anything else 

I also have the same size sprocket wheel /chainring (not sure if that's what it's called) listed separately, will combine shipping costs.