Hi Shreck,
I apologize. You were just asking about the marks not a identification of the gun. They do appear to be private Tower proofs, which gives a earliest date of 1751 or so. By that time, locks without pan bridles would be generally used on cheaper livery and trade guns. The pistol by Stanton that you linked to must have been made before 1766 when Stanton died. Jonathan Stanton took over the business from William Turvey in 1745. Anyway, if your pistol is related that narrows dates from 1751-1766. Do you have any context or story about this pistol that you are willing to share?
dave