I found a bottle in my grandmothers attic. It says Ferro - China - Berner Co. New York.
It also says to be used as a tonic. Labels are in excellent condition. Still sealed with product inside.
Carlyn Rings For Bitters Only lists over a dozen Ferro China bitters.
"A variety of bottles are lettered Ferro China. Common usage calls them Ferro China Bitters. In reality they are identified as bitters only by their labels."
I don't think they are true bitters but more like Angostura bitters, an after dinner cordial in my opinion.
What height and color for your bottle.
There are two New York bottles listed Ferro China.
Five bitters (stomach, kidney & liver, blood) San Fran CA,
under Ferro Quina Bitters.
relationship between the two companies is unknown.
These bottles were made in the early 20th century. Since they were manufactured in Europe where glassmaking was "behind" that of U.S. glassmakers, they have characteristics that are more typical of U.S. bottles made 20-30 years prior.
I've always wanted to try the contents, but too chicken...so far...