I've noticed that historic ads often contain periods (full stops) in the headlines (this is no longer common practice). An example is a ghostsign (old faded building sign) in Cleveland, Ohio, that reads:
[Name of Company]. Millinery.
My question: When were periods commonly used in headlines and after company names, etc., and when did that come out of favor?
I've noticed that periods also sometimes appear in mastheads and newspaper headlines, historically, and that periods don't seem to show up in ads in the late 20th century or early 21st. I'd like to try to date the ads based on the punctuation. I know that David Ogilvie advised against using periods in ad headlines in the 60s.