Upon further scrutiny, the 'cut-away' receiver shows the Proof "P" and index mark on the front edge of the receiver ring.

This would mean heat-treat and 'Proofing' were performed on this receiver.

I would conclude the "cut-away" machining was performed on regular heat-treated Krag parts.

Also Note: The forearm 'wood-line' is lower than would be seen on a normal stock. The 'P' and Index marks are usually concealed by the forearm.

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