This is a picture which shows both the narrow groove and the wide groove CD 156.1 American's. One can see that the two styles are very different. The one I call "narrow groove" has a very sharp dome edge and wire groove edge while the one I call "wide groove" has a much more rounded dome and wire groove edge. I feel that a separate CD number might be needed - e.g. CD 156, 156.1, and 156.3. There is already a CD 156.2. Also, note that the CD 156.1 Postal is different style than the two CD 156.1 American's shown above. What do you think? Also, I feel that the CD 156 might be a style which was only used exclusively on Postal Telegraph lines while the CD 156.1 American could have been used on both Western Union and Postal Telegraph lines. Does anyone have any information or have you found any CD 156 styles on a Western Union line?