Thanks,
Sorry I never realized I put "Cooper" instead of copper. It isn't dirty, it actually gleams. If you pull the face off it is the same color on the back as it is on the front. Since all of these came from a museum which had a number 4 singer, and a first year Wilson, not to mention 24 other pre-civil war machines; I think I actually might have some type of experiment or maybe as stated before something that came as a result of shortage of material. We are going to see the sister in 2 weeks and go through the 5 boxes of paperwork and it may solve the mystery. Thank you so much for the information though. I really appreciate it!