When S'G' finished off the old Irwin Pedersen contract serial numbers, they then took a chuck of serial numbers from S.G. to continue to make carbines. This ended by the end of December 1943 when S'G' then stopped making carbines.

Your carbine has been through a typical rebuild post war which updated it to the last improvements. The rear sight was changed and the adjustable rear sight was added. The PI on it means it was made for Inland. The type 3 barrel band was added then too and the one you have is a pate war/post war update with the bayonet lug. The rotary safety was changed as was the magazine release.

When your slide came off were you pulling back on it? If so were you also perhaps pulling upwards at the same time? If so this could account for it coming off the track as it's only should be pulled straight back.
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