Originally Posted by non-fixie

Thank you! That'll give us something to go on. The Titan bars and stem are not a surprise, and would have been my guess, as they were popular at the time. From the late forties to the late sixties they were the gold standard in these parts, it seems. The bars can be dated by the world champions mentioned on them. Rick van Steenbergen became world champion in 1949 (Schotte in '48) so these bars would be 1950 or later. If the script is facing the rider, they could be original to the bike, if not, they would be later replacements.

As for the rest of the parts, I would suggest at looking at what Dutch pro riders were using in the early fifties. You should be able to find lots of pics, as this was a very successful period for the Dutch in racing. Talented frame builders, talented riders and a decent organization led to a Tour de France win in 1953 (when they were fielding national teams) and a Tour de France start in Amsterdam in 1954. RIH and Locomotief were the two biggest brands providing the racing bikes.

Off the cuff: I would expect Simplex Tour de France derailleurs, Weinmann brakes, a Titan seatpost, a Brooks saddle. Stronglight bottom bracket and cranks. Not sure about the wheels. Parts were generally French, Belgian or Swiss. Italian is far less likely.