It appears some crude repair work has been done in the past - (pin or nail marks by the trigger-guard)?

IMHO - It would be worthwhile to clean up any bad inletting and strengthen old repairs with 'stock-bedding epoxy mixture.

(The rear of the side-plate and a small area of the magazine box seem to be pressing unevenly or in contact with wood [red arrows]. The receiver tang also seems to be 'standing proud' [black arrows]. A bad stock/action fit may have facilitated the cracks & splitting).

BTW - It appears a small area of wood was removed, between the magazine-gate and bolt handle, probably to clear the elevation-slide of a commercial 'peep' sight [black triangles].

As a matter of interest, your stock is a model 1899 carbine stock of Italian walnut. 'Acceptance Cartouche' stamp is "J.S.A. - 1900" - (Joseph Sumner Adams).

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