Lee Enfield No 4

So, you have a serial number. That's NOT scrubbed clean then...

Yes serial on the right side but no markings at all on the left side.

I suspect like Peter suggests, the charger bridge was re done and then the whole affair was ground clean and refinished. Possible nothing sinister took place at all.

Second picture, post 10: is that an RFI factory stamp next to the "C"?

If it is, then you have a likely answer to why there are so few markings on the rifle.