Here's the chart again so you won't have to click/scroll back to find it. Notice the dates of the plants that have double-digits with a 1 being part of it. I suppose its possible (as there have been a few exceptions found) that this and all of the other charts are not 100% accurate. But I still consider this one as the best of those currently available.
Bob those two bottle machine photos are greatly appreciated, I'm sure I could have Googled the info and found it but I never took the time. I was curious as to how they got the same amount of liquid glass for the blow and the other details pictured, an eye opener for me...[]
It would appear that if we could find this book it may shed some light on things Bob...
"These caps were often found on soda and beer bottles that were shipped overseas to the troops. An example of this can be seen in Henri-Paul Enjames' book "GI Collectors Guide" Volume II p139."