You posted this a decade ago but I still happened across it while looking for info on my gg grandfather Mathew Carr recently. He came England to Dietz to mine coal (like everyone there I'm sure)in about 1907. In 1909, he moved to Roundup MT to mine there. It looks like quite a few of the men did that. I wonder if you searched Roundup if you might find him. Musselshell is the county. Hope you've been able to find something more in the last 10 years.