An interesting rifle! The lever-detachable magazine floorplate is a modification often found on pre-WW1 Suhl made Mauser action rifles. It probably gave Mauser the idea for the hinged, lever opening floorplate.
The stock is definitely of Mauser post-1912 shape, more likely even 1920s – 30s. Is there a serial number stamped in the barrel channel? Does the buttplate show the earlier WFM logo or the post-1926 MAUSER banner?