Interesting! I have about seven pistols in my database in the 43,000 range and none have any test proofs or WaA marking except for one in the 43900 range that Charlie reported to me at one time. Your gun does not look like it has seen much action, unlike most of the guns that I have encountered with (later) added WaA markings or testproofs. I recently found out that the Belgian arsenals were treated in the same way as FN's warehouse. The captured guns were moved and not marked. It looks indeed like yours was most likely never issued to any Belgian officer or soldier. I am not sure why yours would have the test proof on the triggerguard.
Sorry that I am not more detailed.
Anthony V.
Sorry that I am not more detailed.
Anthony V.