This is the M1850 Prussian Cavalry pistol. It was not converted from flintlock, and although dated 1850, it was already obsolete by the time it was adopted by the Prussian army. I have one on my website
https://www.oldgunscanada.com/prussianm1850sn1348 priced at $1550. It's been cleaned and restored, unfortunately but still a fine specimen. Yours has regimental markings on it suggesting it was issued to the "Landwehr", probably long after it was removed from cavalry service. It has also been modified. The barrel has been shortened, and (as already stated) the hammer has been replaced. The front sight was added probably at the time of the barrel shortening. This may have been a job done at the arsenal before it was re-issued to the Landwehr. In this condition, if it is functional, you may get $500 to $800 for it. I hope this helps.