Turned Capital letter L (pointing to the left, with serifs)

[Michael Everson]

On 4 Jan 2016, at 21:33, Frédéric Grosshans <frederic.grosshans at gmail.com> wrote:
> 
> The Greek letters in particular have a pretty standard shape, and I don't see why this symbol would be the only geek letter using a fancy cursive shape. Even the Latin letters used standard shapes ( italic, roman, a few capital fraktur). 

If he uses a regular tau for anything else that would be the reason.

> That said,  I did not spot a tau in the text, while most of the Greek alphabet was used. Could "7" be a standard shape for tau in 1809 Hamburg?

It’s a standard variant in many older Greek typefaces with ligatures. 

Michael Everson * http://www.evertype.com/