Antique portrait miniature c.1820s

The hairstyle of the elegant female sitter suggests this miniature portrait dates to the 1820s, the latter half of the Regency period. The frame appears to be a faux tortoiseshell with a foliate engraved metal ring framing the portrait itself. There is a signature that I've been unable to make out but what looks like an umlaut suggests the possibility of a Germanic artist. There is additional writing in white that is even more difficult to decipher so sadly her identity has been lost to time. Nonetheless, this lovely miniature portrait offers a glimpse into the past and would make a stunning addition to a collection or a cabinet of curiosities.