Jerry,
I believe you will find that there was or is a big difference between "colchester clausing" and "atlas clausing". At one time I owned a 10" atlas clausing that was made in Ottumwa, Iowa. The colchesters were probably a better machine,for their price they should have been. The one thing about the colchesters I was not fond of was that the half nut threading lever went the opposite direction of the American machines. If you were not paying close attention things could exciting when you got up close to a shoulder. That was in the late 50' and early 60'.