They generally don't go for much and the price really does depend on condition. Photos help. I paid $38 for mine a few weeks ago and it was made in 1930 for smokeless ammo. B668 would be an earlier black powder pistol. Do not fire it with smokeless ammo. There are patent dates on the pistol and whatever is the last patent date stamped puts you in the ballpark of when it was made. Depending on condition you could probably get a bit over $100 in really decent condition.
Did some checking - serial no. B668 would have been made in 1898.
Actually, it's in quite nice condition. I suspect that if you sold it you'd might get around $150. There are quite a few available which is why the price isn't higher. As for firing it - if you find some black powder rounds I suspect that it would fire just fine
A black power model made in 1898 should have a safety lever in the trigger, and front of trigger guard should be retained by a screw and not a cross pin. According to the book, these changes were not made until the change to smokeless powder in 1909. And the B serial number prefix was used again 1909-1918.
The type of mainspring will determine which it is:
If a flat spring, it's a black powder model made before 1909,
and if grips are original, the owl on grips facing toward the barrel indicates it is.
But an adjustable coil mainspring means it's a smokeless powder gun made in 1909.