Here is a few more Pictures.
The barrel has on the side a crown and S.t.m.G. N22gr then in another spot on the side the same thing but 18gr.
Around on the next side down is the letters R G and U each with a crown over them. Then 10.5mm with a 60 under that and 9/28 under that.
More on the bottom B G U and E each with a crown. a serial #
also 10.75 X6Q
and a gs with a circle around it.
All interesting stuff