When does the circular zero arrivein cold metal type? With the first arabic numerals or afterwards?
Eben, the [[http://en.wikipedia.org/wiki/Arabic_numerals|Wikipedia article on Arabic numerals]] refers to a book that looks like it would have your answer.
Pretty early, I believe, and I think an interesting thing to research would be whether this or similar methods were used to differentiate o and 0 in manuscripts prior to the advent of type. Arabic numerals, including zero, were in use in parts of Europe in the 12th Century, and the similarity of o/0 was causing problems for scribes long before it became an issue for printers. Charles Burnett's The introduction of Arabic learning into England has some discussion of this, and illustrations of early English manuscripts incorporating 0.
Modern accounting was largely invented in renaissance Italy, and I would be inclined to look to see how 0 was written in manuscripts related to bookkeeping.
Ah, just remembered that I have a copy of G.G. Neill Wright's The writing of Arabic numerals, which includes some charts showing development of mediaeval numeral forms in Europe. There are certainly examples in which the 0 seems consciously drawn as a circle, although without so obvious a change in contrast as seen in type. In some cases the circle is quite small relative to the other numerals.
It is interesting to note that the inclusion of a slash to differentiate the 0 is very common in these mediaeval forms.
For quite a long time, even to math academics, zero was stubbornly considered "not a number". This is probably why the circular nought, in its function as a "placeholder" in decimal notation, was consciously drawn more like a symbol than a numeral. The no-contrast treatment often found in old style figures is in keeping with other mathematical symbols like +, =, >...
Great stuff all. Thanks as always. Probably the next step is to ask Hendrik Vervliet what he knows about specific type faces.
You may have seen this on ilt...
"When does the circular zero arrivein cold metal type?"
The near perfect circle? The zero made by a round punch?