Gene,

It bears 1904 to 1925 Birmingham proof marks and with that serial number is clearly a Riggs-Reilly.

As 13/1 it should measure .719” (+?). As the bores are now .728” it has clearly been honed since proof and is now marginal even though the wall thicknesses are good.

Either the case has been re-labelled or it is from an earlier Reilly gun?