Very nice rifle.
I'd guess it's FN made & marked for the European market after 1956.
FN made about 200,000 of these prior to 1956 and ser#'d them as such. They started making them around the start of WW1.
No prefix to the FN serial number,and nothing in the ser# to denote the caliber of either 22short,,or 22LR. The imports for Browning Arms Co did so later on though.
Then in 1956 when Browning Arms Co decided to import the model under their name (not just with the Browning Pat mark on it),,the USA imports were given a separate serial number range.
Plus USA imports were given an 'A' prefix for .22 short,,and a 'T' for 22LR. ( with a few exceptions being found of course).
When this occured in 1956,,FN started serial numbers all over again for their production of the rifle they produced for sale under their marking. They still had the agreement of European sales and some other parts of the world. Something JB had done with FN on other agreements when selling the rights to his patents.
(That's why the Remington 24 was licensed for production & sale in the USA , as was the Remington 08 and other Browning patents.)
I don't know how long FN continued to produce the FN marked 22auto for the Euro markets but it was at least till 1966.
Your rifle is one of those post 1956 FN production/ FN marked rifles for European sales I'm thinking.
I don't recall any ser# lists on the FN produced rifles. The wheel sight was used in a certain production time. That can be a clue. I can't remember what those productions years were right now.
The Grade I engraving pattern is a little different in the early post '56 FN marked/production. This one has the later style. But that was changed only a couple years in,,maybe '58 .
I believe the trigger in your gun is the later type, used from 1960 onward.
That's the best clue I see w/o having a ser# chart.
Been a long while since I looked into these, perhaps the ser#'s are available now with all the new books & collector info out.
That's about the best I can do right now.
Just a beautiful FN rifle as I said. Would make any one proud to own it.
added,, the Belgian proofs have year/date/code with their mass of stampings. Should be an underlined letter. Don't know why I didn't think of this before.
Markings may be on bottom of bbl usually under wood,,on recvr, or both. Bolt should be proofed also.
They were using Greek letters through the 50's and til '61. Then started with small letter 'a' underlined in '62 and went from there year by year.
Here's a chart on this website,,scroll down to 'Belgian Date Codes'
http://damascus-barrels.com/Belgian_All_Proofmarks.html
Two charts,,one is in cursive that is used occasionally so it helps to see what you're looking at.
I have found some Belgian proofed firearms w/o the date code stamped. You're back to guessing by the guns features at that point.
There is also the Proof Controller marking. That will be a letter with an (*) over the top of it. Not to be confused with the DateCode. It can help sometimes narrow down the mfg date, but the Controllers were sometimes employed for years and years there. Their marks were sometimes re-issued to others also so you have to be aware of the firearms general mfg time to assign the Controller mark.
Proof yr is a good indication of Yr/mfg. They went right to the proof house in Liege as soon as possible as the laws didn't and still don't permit sale w/o Gov't proofing.