The barrel looks pretty shiny inside and it looks like it has some sort of a lighter colored metal liner. I've seen pictures of rifles with the mum on them and this one doesn't have that but also doesn't look like that area has been filed. I don't know what the caliber is. There are some numbers on the end of the bayonet handle and a symbol on the bayonet blade next to the handle.A close up picture from the rear sight to the bolt handle would help with placing a value. Also a close up picture of any writing or symbols both on the bayonet and the rifle would help as well.