To me, this action and barrel lack all the earmarks of a 1930s Mauser, Oberndorf commercial action:
I have yet to see an original 1930s commercial action with a round instead of teardrop bolthandle and a short striker nut, features that appear on late commercial actions from 1940 to 1945 only.
The serial number 1124 does not fit into the Mauser commercial sequence. A 1930s Mauser number would be in the 110000 to 116000 range. Such a Mauser number would be on the underside of the receiver, behind the recoil lug, on all commercial actions sold to other gunmakers. Here the receiver lacks the typical script G or Q worker’s and the ornate "gothic letter" marks usually found on such actions. Instead, there is a plethora of worker’s marks as usually found on receivers made by the government arsenals up to WW1. Then there is a German civilian crown/U view mark under the front end of the receiver ring.
The barrel dimensions in mm are marked on the barrel at right angles. The Mauser factory put this information on lengthwise.
As it is a standard length large ring action, it is a Gewehr 98 action left over from WW1 production, likely barreled in Suhl and bought in by Rigby from a source other than Mauser. The “commercial” appearing triggerguard does not change my opinion as it is just a matter of filing to reshape a rough military undermetal to this form, a common feature of Suhl made Mausers.