I've been searching for some kind of birth/baptism record for Mary (Marie) Baumgarten, daughter of Samuel Christian Frederick Baumgarten (c1729-1798) and Mary Joynes (c1729-?), who was later the wife of Gaspard Weiss (1739-1815), for ages now.
I have a record (from the Burgerbuch of Mulhouse) which suggests that unlike all her siblings who were apparently born in London, England, she was from Nassau-Usingen (though perhaps not born there). I still was looking for some vital records for proof of this though. According to the marriage allegation for Gaspard Weiss and herself, she was born around 1755.
In the last week or so, Findmypast has released 3 million new Westminster records onto their website. I'd previously found lots of records for Baumgartens and Joynes and other related families in Westminster so I did some searching and hit pay-dirt! A "Mary Baumgarten" was baptised at St Margaret Westminster on 15 August 1755. She was recorded as the daughter of "Saml. Christian Frederick by Mary", born 21 July 1755. Mary's sister Charlotte was baptised in the same parish in 1757.
So the question is: was she born in Nassau-Usingen or England? I don't think there's likely to be a way to ever know that for sure, as I've never found any shipping records from that time, which could tell us that a (newborn?) Mary Baumgarten travelled with her parents across the English Channel to England... It does seem possible that there might have been enough time for them to get from Nassau-Usingen on 21 July to London on 15 August though. We'll probably never know...