Well, double damn. I have a Gibbs .450/.400 in my database from 1905 that is 10602. However that gun has pre-1904 London proofs. Yours are post 1904. I do have an Army & Navy .450/.400 with an estimated date of 1905 that is 11170 and an Evans .400/.360 that is 11397 that was ordered in 1906. Kinda thought yours would be a bit lower.

I have no idea what the 1 and 2 mean.

Really nice rifle Curl.
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