"...commercial SN's, which are 20000 to 215000..."
Vanderlinden shows pistols 250254, made in 1934 and shipped to the Danish police (P.K.27 Nr. 4) June 26, 1935*. He also shows two other Model 1922 shipped to the same buyer, No. 263935 (Rplt Nr 995, no date given) and 267177 Rplt 2581, from c. 1938. So Model 1922 numbers definitely exceeded 215000 before WWII. Extrapolation is dangerous, but if 250xxx was 1934, and 267xxx was 1938, the production would have been 4,250 a year. If we can assume that production increased as war approached, 283xxx seems possible by the time Belgium was invaded on May 10, 1940 and 288xxx-289xxx could well have been in the factory at that time and taken by the Germans (WaA 613 marked).
So, a date of late 1939 seems likely for a pistol numbered 283xxx.
FWIW, the Germans seized pistols in both 9mm Kurz and 7.65 Browning, but produced/had produced for their use only the latter caliber, since the 9mmK was not in their military/police supply system. Of course, it could be obtained but, like the .38 Super in the U.S., it was not an official caliber.
*Unlike the Dutch army, the Danes did not insist on their own serial number range, so those numbers are in the commercial range.