I am really interested in purchasing an original unit of both of these knives. I am not really interested in a replica and would like to get an original.

I have looked on eBay and I have a hard time ponying up the amount of money they are asking for something that I cannot completely trust to be authentic.

Does anyone know of a trusted source of collectibles such as these?

Also, what is expected to be paid for such fine historical collectibles?

Unfortunately as a collectible item you are going to pay what the market dictates. A few years ago they were fairly reasonable and could be found in the $300 range. Now I seem to be seeing them in the $500 (that's probably even low) and up range.

You can try http://www.usmilitaryknives.com/knife_sale_page.htm if you are looking for a collectors page.

The M1917s really have not gone up too much in price.  They also are not faked too much but there is one company who makes reproductions that are very good. Most common makers will be LF&C and A.C.C.  There are also two types of knuckles on them.  The flange style (ACC common) and the pyramids (LF&C common). $300-400 for a nice one with scabbard.

Common things to look for are a scabbard with tip and throat that are tight to the leather and a blade that has not been re-tipped.

The M1918s have gone up quite a bit.  As such they are now heavily faked.  Most of today's replicas are nothing like the real deal but the ones from the 1980's were very good and can still be found today with spurious markings.  There are four makers and only two of them are common. LF&C and Au Lion are the most common and the Au Lion was likely the only one to serve in combat in WWI.  You also have HD&S and Onieda which are crazy rare and also heavily faked.

Things to look for on these are the scabbard prongs that are intact, correct scabbard to the manufacturer, correct blade, correct pommel nut.  Markings are the correct font and spacing. Handle is bronze and not brass.  How much of the black finish remains (Au Lions were not finished this way).  $600-1200 for one of the common makers.

These are the only two I have other than a 1980's repro I bought back in '87.
The M1917 is an LF&C that was a gift from my ex wife.  She paid $275 back in 1997.  The M1918 MkI I picked up at a Petty Officer First Class Leadership class from the guy who was sitting next to me.  Now do not cry,  I paid him $20.  He wanted $5!  Also an LF&C with the correct scabbard but with both hooks broke off.

Wow, both of y'all have been very helpful.
Thanks for sharing the photo and story. That's amazing chance encounter.

Unfortunately, the USAF does not have the same culture of weapons and history. Everyone I work with only talks about videogames!

What is commonly called "the 1918" trench knife is actually the Mark One, 1918 trench knife.

The Model 1917 and Model 1918 are the spike bladed "ice pick" type knives with walnut handles and steel knuckles.
There are several variations of these weapons, but only two versions of the Mark One, one made in the US and one made in France.
US Mark Ones were made by Landers, Frary & Clark, and one much less common made by Henry Disston & Sons.
BEWARE of a Mark One marked as O.C.L. Onida Community Limited.  These are almost always fakes since O.C.L. may not have made more then very short test runs of just handles.

Contrary to popular thought, the handle of the Mark One is actually cast bronze, not brass.  Only the much lesser quality French made Au Lion Mark One has a cast brass handle.

You can find original Mark One knives at big gun and knife shows.
Online I know of one site that has the real deal but also real sporty prices:
Great War militaria usually have Mark One's and the spike bladed Model 1917-1918 "knife".
If they don't have something in stock, if you contact them they may either be able to get one for you, or put you on a waiting list.  At least they're experts and don't sell fakes.

Great War Militaria

Recently there were several Mark One's on Gunbroker.com under the Knives and Swords section.
These looked authentic.

Here's a site with good info on detecting fakes:

Military Knives

Another source would be to do a search for online militaria sites.  You can check the For Sale areas or advertise for what you want.  Like everything online, people who have a lot of posts are usually legit and don't sell fakes.

The spike blade Model 1917-1918 is much less faked, and with a little research you can usually spot a fake from the poor quality and differences in finish.
There are excellent fakes of the green leather and steel Jewel Belt Company scabbards being made and it's harder to detect fakes.
"In most cases" if you buy a Model 1917-1918 spike blade knife it's the real thing.
Originals were made in WWI and surplussed off in the 1920's so they tend to have a well-used look.

Places to look for these is ebay and gunbroker.com.  These usually don't have an original scabbard, and may have a modern replica.
You'll see a lot of these with "expedient" sheaths made of canvas or leather.
While the Model 1917-1918 was not officially issued during WWII a lot of them were dug out of Dads foot locker and given to sons off to WWII.  Often the sheaths were missing or rotted so some sort of replacement was common.

You may see altered Mark One knives.
It was fairly common during WWII for the round guard to be cut off one or both sides so it would lay close to the side and not get fouled in gear.
Often these knives will have expedient leather sheaths purposed from hunting knives.
This was often necessary because one or both scabbard prongs were broken off.

Prongs got broken because the soldier tried to bend the upper prong down so it would mount on a pistol belt.
The upper prong was bent upward so it could be inserted up into the top grommet of a cartridge belt.
Many paratroopers preferred not to use a cartridge belt and broke the prong off when it was bent.

Another cause of broken prongs was because many people in WWII didn't know how the scabbard was to be attached to the cartridge belt.  It's supposed to be mounted INSIDE the belt and when mounted on the outside, one good tug would break it off.

Last year I stumbled across a French , Au Lion , Mark One.
Unfortunately it had no handle.
But it does have the little spiked nut to hold it on and the scabbard. And it's all in pretty good condition.
Asking around I heard the French Mark One is harder to find and somewhat less desirable.
I paid .50 cents for it.  I had no idea what it was when I bought it. It was the scabbard that cought my eye.
And the easily seen lion on the knife made me think looking it up on the internet when I got home should
Come up with a manufacturer.

I made a modern version of the 1918 trench knife while I was in Iraq. I had an M7 bayonet and a Chinese copy of the 1918, so I cut the latch off the M7, tacked a 1/4x20 bolt on the end and mated it to the brass knuckle handle. I shaved the sides of the handguard, put it all together and had a knife that caused a lot of nervous looks from the Iraqis. They didn't care if we pointed machineguns or rifles at them, but show up with a pistol or a mean looking knife and they started to get a worried look on their faces.

I gave that knife away to a guy in my unit because Navy Customs probably would've confiscated (stolen) it on the way out, and I didn't want the hassle. It's probably still floating around over there somewhere.

my grandpa had one... he cut the knuckles off so it was easier to use as a knife. i don't know if that was a common thing or not.

It was not uncommon during WWII.

Few if any American made Mark One knives made it to France in WWI, so most were issued in WWII to paratroopers And Rangers.  many people altered the Mark One either to make it more usable for modern combat, or just to customize their knife.

Many had one or both sides of the round guard cut off so it would lay flatter against the side, or so it could be carried in a leather sheath after the steel scabbard prongs were broken off.

Some users cut the knuckles off leaving finger grooves, so the knife was easier to use.

It's funny you mention that. That was my experience also, that the Iraqi's didn't seem fazed by my M16, but pull out a knife and they got edgy.

I recently read a book by an Iraq veteran and he said that what really got attention was when you pulled a pistol.

He said that rifles didn't impress anyone since everyone had an AK.
But due to Saddam's thugs, the Iraqi's got very quiet and nervous when a pistol was drawn because when one of the thugs drew a pistol someone was GOING to get shot.