Without more pictures, including markings, it is not certain to say.
It bears a strong resemblance to two British naval pistols in Gilkerson's 'Boarders Away Vol. II - see pages 245 and 246. The lock & trigger guard have a very similar profile as does the overall architecture. Interestingly, the pistols in Gilkerson are dated 1720 and 1808 and vary only slightly from each other in spite of being nearly 90 years apart. After the Napoleonic period, the RN adopted a shorter barreled pistol.