Since we have a run on Bulova stamped cases on the outside that look like this,
Here is some info I found on Keystone Watch Case Co. None of their trademarks look like above...
Here are Bulova's trademarks...
American Standard trademarks..
And if you though buying a Warranted 14K US Assay marked case was the way to go, Duber Hampden says NOT!!! ; )
If you come upon any info that will help prove or disprove any of this, please add to it.