Whopper Stopper; welcome!
You spoke of genuine manufacturer "repros" or outright fakes with no stamp markings?
-http://www.usmilitaryknives.com/camillus.htm
-http://www.usmilitaryknives.com/ka-bar.htm
First thing you gotta know is that the current U.S. Gov. Issue (USGI) kbars are stamped with a "US" mark.
Forget real deal WW2 kbars, as these are mostly sold as and when they become available from individuals who want to dispose of them.
There are differences between "wartime supplied", in opposed to what is now.
The kbars currently USGI are either from Ontario Knives,
Read "Mark 2 Markings"
-http://www.usmilitaryknives.com/knife_knotes_3.htm
Read "New Purchases"
-http://www.usmilitaryknives.com/knife_knotes_9.htm
Current Ka Bar Knives are not made to government specifications.
Read "More on the Black "Issue" Ka-bar"
-http://www.usmilitaryknives.com/knife_knotes_10.htm
So are considered kbar replicas unlike the WW2 Ka Bars
How much a difference this all makes to the common everyday user or serviceman is yet to be listed for a fact. But basically I won't be too surprise to find this stopping anyone in the military or otherwise to buy one "off the shelf" (regular commercial variety). You could to.