Your gun is interesting Hal. It is a Pieper Diana Breech. Here is a Pieper J. Manton & Co. Modified Diana with another (odd) breech treatment
It should be an early gun, but the proof marks date it to 1910-1920. Pieper was known to use 'D.C.' for some reason.
The R barrel is Cylinder with a bore of 18.2 mm = .717". The L muzzle constriction is 17.6 mm = .693" = .024" or IM
Looks like a 'gunsmith' pounded on the barrel lug to tighten the FE?
And the L firing pin may be a nail?
Note Dave's Sears ad lists "Royal Damascus Finish" meaning Faux Damascus, likely
décalcomanie over decarbonized or fluid steel; Pieper was reported to use Siemen-Martin from Cockerill which was good stuff.
Your gun looks to have the same process.
This is a T.
Parker in the 1895 Montgomery Ward catalog with "Imitation Damascus"
T.
Barker in the 1899 Sears catalog with "Royal Damascus Finish"
T.
Barker in the 1902 Sears catalog but the illustration clearly says T.
Parker. It also has "Royal Damascus Finish" over Sears' tradename Wilson's steel which was probably decarbonized steel
Tomas Barker in the 1902 Sears catalog with "Imitation Twist"