Nr. 4 Mk 1 Barrel Markings - Need help

I recently inherited a Nr. 4 Mk 1 after my Father-In-Laws passing and have been researching as much as I can about it. Unfortunately I do not know the story of how he came to posses it.
I am pretty sure by the markings that it is a 1944 ROF Fazakerley rifle and the markings on the stock under body forward match the rear band (MB21601).
What I can't find are any reference to "Barrel Markings. I have attached a photo of the barrel tip and those markings stamped into it.

Any information would be greatly appreciated.
Thank you,

Quote:

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Originally Posted by LA Gman

I recently inherited a Nr. 4 Mk 1 after my Father-In-Laws passing and have been researching as much as I can about it. Unfortunately I do not know the story of how he came to posses it.
I am pretty sure by the markings that it is a 1944 ROF Fazakerley rifle and the markings on the stock under body forward match the rear band (MB21601).
What I can't find are any reference to "Barrel Markings. I have attached a photo of the barrel tip and those markings stamped into it.

Any information would be greatly appreciated.
Thank you,

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The muzzle markings are UK Civilian Proof markings, the tests were undertaken by the London Proof House

Calibre = 303
Cartridge length 2.22"
Test pressure = 18.5 tons per square inch

Side wall markings

No4 Mk1
ROF(F) = Royal ordnance factory Fazakerley
Date of manufacture = April 1944

Butt Socket marking
Serial number = MB21601

Thank you so much. I really appreciate it!
I can't wait to fire it. I had it cleaned and inspected already.

Quote:

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Originally Posted by Alan de En
field;454415

The muzzle markings are UK Civilian Proof markings, the tests were undertaken by the London Proof House

Calibre = 303
Cartridge length 2.22"
Test pressure = 18.5 tons per square inch

Side wall markings

No4 Mk1
ROF(F) = Royal ordnance factory Fazakerley
Date of manufacture = April 1944

Butt Socket marking
Serial number = MB21601

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