Here's a pretty typical Dickert barrel signature.
Note the small crossed tomahawk/arrow cartouche with the four surrounding punched circles between the J and D. Most signatures seem to have this, but not all. Also notice the wide spacing between the J and the D. This also seems to be typical whether the signature has the cartouche, or not.
All the Dickert signatures I've seen have been engraved. The cker on the lower flat of your barrel is likely the barrel makers name, but I'd be doubtful that it stands for Dickert.
On your barrel, the 1st letter is obviously a J, and the 2nd letter looks like an M. But it also looks like there was an older/earlier letter that was purposely mostly obliterated by the M. The 2nd letter could have been a D. But a J D could have been many makers, and doesn't necessarily mean Jacob Dickert.
Just my opinions of course!
John