My Dad's WWII Luger...

[Zamo]

Don't sell it. There are better ways to come up with cash. Sell the dog, sell the girlfriend...
Once it's gone, it will NEVER come back. Would your Dad approve of your selling it for whatever reason you need the quick cash? Do you have any children that might one day think it's pretty cool? This is a family heirloom from a time in history that now belongs to the ages. They aren't making any more of these.
If you're determined to sell, put it on Gunbroker with a $1500 reserve. It probably won't fetch much more than that, but these days, it's robbery to give one up for less, unless it has mismatched parts, or serious blemishes, rust, pitting, etc.
Again, I don't think you should sell it. Ten years from now, you may be flush with money, and you may actually go out and buy another Luger...but you'll pay much more, and get less, and it won't be "Dad's".