Thanks guys for the offers to assist but it looks like (for now) this will remain a little mystery for myself as I am incapable of producing decent detailed photos with a cell camera.
The magazine floor plate clearly has the last 4 of the serial number written on it under the new finish but now, with a properly jaded eye, I am not convinced this was done by a electro-pencil and was probably written by the refurbisher (with a ink marker?) to ensure the “right number” was stamp on the part.
The bolt body and bolt sleeve clearly both have “cleaned up” electro-pencil markings under the new finish with the bolt sleeve being the last 3 (though 4 are “properly” stamped on it where expected) whereas the bolt body electro-pencil markings are not so clear but appear to be the last 4 though the 4th character is tough to read.
This K98 was obtained as a refinished and refurbished RC (though the “X”, if any, has been scrubbed) with forced matched parts where needed so odd or mismatched parts is no surprise. The “why” of the matching electro-penciling of the serial on the bolt, then trying to remove it, is a surprise but after 75 years I guess there is no way of telling the travel tale of this gun - both before and after the refurbishing - and whose hands it may have been in.