Argo,
This gun has a bunch of DIFFERENT serial numbers on it, but they are all in the 3500-3900 range-4 digit, no letter prefix.
Further complication is that the Halifax was not cataloged that early, and I suspect there was but one, not the 3 and 4 number grades that came later. The Halifax grade guns tended to come and go with the ups and downs of the economy.
As I stated previously, I owned a V20 Darne that was in the 50,000 serial number range and was dated to 1910 by the Darne factory. The number was less important for accurate dating than the signature of the engraver on the gun, and the quality (lack thereof, actually) of the very old man who was still working into his 90s.

The Olds likes gas, good gas at that. There is nothing like the sound of an American open element, dual exhaust, pushrod V8 coming into the cam and the secondaries of the carb, blasting down a freeway entrance ramp, and that makes it all worth while.

Best,
Ted