In either scenario, the result would be a very fine rifle.
Of that I am sure! Thanks for comments!
Personally, I would be interested to chase the rest of (hidden) marks, if any, under the stock, or action, trigger, or elswhere if they could be traced and photographed, to see if we can get more information, and to put in use some proof marks data base, that I have available.
Germans are very detailed in their proof marking as well, and some german marks would be interesting to see if there are any at all.
Various German firearm proof marks: pre nazi era, nazi era, and post war era can also be easily identified (nobody wanted nazi eagle before or after the nazi period), so basically this is what I would be interested to check, if the photos could be provided.
The nazi era of proof marks started by contemprorary law as of 1939 and lasted till 1945. From 1945 till 1952 - there was no gun production in west germany. During ban of production period, making of rifles was banned, but rifles were alowed to be used (for hunting for example) but barrels had to be imported. (this indicates possiblilty of belgian barreled action, stocked in germany in that period?)
So that could be one lead.
And after that, after 1952 new standard proof marks applied in west germany. So German proof marks, if any could be found, could give a good estimate of rifle wintage
Eastern Germany was under differnet rules, and immidiately after the war, 1945 started production of smooth bore barrels, under same 1939 mark system but without eagle. Ok - this is already different subject. (Heym started their legacy in Suhl - east germany, but restarted in west germany after 1945)
Second lead could be:
I am not sure, about pre-WW2 period, but many of the post w. war 2, production of general merchanidise in Germany, and espesially higher quality products were stamped as MADE IN
WEST GERMANY. (1949-1990, untill unification later) and Made in Germany US De-Military Zone 1945 - 1949.
If that is the same case with this rifle, it may be easily pre ww2 production. So, basically this is my 2nd possible consideration, pending any future evidence that OP may provide with better photos, hopefully with some german stamping.
But whatever is the story of that rifle, we need some more detailed photos of the markings.
However, considering all above - Belgian stamping and german production, somehow to me gives the strongest indication of early post ww2 wintage.