Difference in Noga Dial Gage Holders

I don't know about the two speed vs the one speed Noga holders but I have two Noga indicator holders that have one big knob that loosens and locks the arms for coarse placement and there is another adjustment on the clamp that holds the indicator for fine adjustment. I love these tools. They position the indicator so fast and hold it so ridgid that after I bought the first one I hadda buy another so one is always used on the mills and the other on the lathes. I paid $85.00 bucks each for them over 10 years ago and they get used every day. They will hold a travel dial indicator by the round and a dial indicator by the dovetail. I can't say enough good about them, they work so well. ERS