What are British coastguard flintlocks with tower and GR marks worth?

Answer 1

The tower mark is the Royal Armoury (Enfield) and the GR is King George (George Rex, latin). Since it is GR instead of GRII or GRIII I will assume (perhaps improperly) that your firearm was produced during the first George's reign, 1717 to 1727 but it very well could be from as late an the Napoleonic period. Your claim that your weapon is a "Coast Guard" peice is troubling as the establishment of that service did not occur until 1829, although older weapons were issued to that service from 1821 on when it was known as the Protective Waters Service. Since the provenance of the firearm is questionable, and the word flintlock can mean anything from a pistol to a longarm, I'm afraid that I cannot, nor can any reputable dealer in Empire militaria, give you a proper appraisal. However, an endfield flintlock pistol in good condition (a difficult thing if the weapon spent any time at sea) could command a thousand pounds (1500 us) upon visual inspection and confirmation of provenance. There are many fakes on the market.