Yes, your rifle has been rebarreled, it was proofed by the Suhl proofhouse in May 1932, 5.32.
In the pre-WW1 days S&S did not need to file off Mauser markings in every case,as Mauser delivered actions to the guntrade unmarked except for the serial number if asked, see Jon Speed p.150. Mauser was the only factory that could sell M98 actions to the trade then, DWM and the state arsenals catering only to military demands, so there was no need to display their name. Any commercial M98 action was of course made by them. Only after WW1, 1924, with the maket flooded with ex-military actions, they applied a small Mauser banner to the underside.