I've looked under a magnifying glass to see any sign of repair, but there is not a trace - all the radii and lines match other Maltbys I have of the same vintage. In fact you can see the same machining marks that run in all directions over the rest of the receiver. The Maltby markings are all quite sharp, so no particular sign that the receiver has been heavily refinished. I've got a crate full of b*ggered & repaired receivers, but this particular one doesn't have the "look" of a repair job.

Like many Maltbys, this one was a bit rough in the charger bridge socket where the wheel of the Mk1 sight lies - so i assume that the rifle was probably one of the many built with a MkII 300/600 flip as standard. Maybe by 1944 there was a lump of swarf lying in the jig where they did the axis pin boring....