Kuduae, the marks under the barrels are as follows;
On the flats: Eagle next to a crown/G, below those is another eagle, then a crown/U under that, followed by a 46 at the bottom. These markings are repeated on both the left & right side flats.
On the barrels just ahead of the flats: Eagle next to crown/G, below that an S in an elongated diamond. On the action flat, there is an eagle over a crown/U. There are no other markings on the rifle apart from the maker/address on the barrel rib.
Does this give you a better idea of a manufacture date? My assumption has been that the 46 is a bore/guage size, much like the English use of the 25 on .577 caliber arms, & that the crown/U marks are inspection marks on the unfinished component parts. Am I correct on this?