Here is the latest update with the Beeker1 website. I have finally acquired another Briot Sixpence of Charles I, this one has CHRISTO on the reverse, the coin is not here yet for me to scan and apply to the website, but is on the way. Coming soon will be a 1627 sixpence to go along with the two 1625 sixpences and the 1626 sixpence already on the site.
For the dated sixpence of James I only lacking is the 1612 sixpence and 1616 sixpence. I would be very interested in locating either of these dates.