Thank you each one and all who gave me information. As a side note Jerry Day tells me that he has a complete article on Rio Grande dual gauge operations coming up soon in an issue of the Rio Grande Modeling and Historical Society's Prospector magazine. I admit that this magazine always seemed overly expensive to me at $8 per issue until I considered that it is 100% material on the Rio Grande and that a 4 issue membership in the society (essentially one year), with associated benefits including the subscription to the Prospector magazine, is only $30. I eagerly jumped at the idea. If interested you can find out more at the Society's web page
www.drgw.org.