No.7 Question

[Magnus07]

Recently acquired the No.7 pictured at the top of page 316 in Mr. Marcot's rolling block book. Was hoping someone could shed some light on the lack of a serial number on the lower tang and the full octagon barrel? The barrel has filled in dovetails at both ends and is marked 22S though reportedly has been opened up to 25R. I appreciate your time and any knowledge you might share. Thank you!