Can someone tell me just what the heck is going on here?!!

[Surpmil]

I recently purchased a package deal of 2 No4 sporterised rifles with full length barrels.
One is a savage no4mk1* with 2 groove barrel that had the bayonet lugs removed, barrel polished and blued and weaver TO-1 mount installed. It’s a shame because everything on the rifle is correct, all savage parts and magazine.

The other is the head scratcher. It is a British made No4mk1 (not mk1*) with intact full length 5 groove barrel. It has certainly seen an FTR at some point. There is a faint British serial number on the wrist and a pronounced Savage serial stamped over top of it.
There is a broad arrow and 1942 stamped just below the safety.
Oh and there is a bizarre star stamped on the top of the Knox.

What’s with the savage serial number??

Any info on what I’m looking at is greatly appreciated!

Imgur: The magic of the Internet

My guess would be that the armourer was fitting a new bolt for whatever reason and the bolt was a salvaged part with that serial number on it and so it was easier to make the rifle match the bolt than to make the bolt match the rifle.
The crappy electro-pencil job on the original serial number allowing such a short-cut(?)

A deeply stamped serial number on a bolt handle requires a good deal of careful peening and filing to prepare the surface for a new number as there is not enough "meat" on the average bolt handle to just grind the old number away or line it out and stamp another.