Any idea where this is from?

It's a standard A2 Stock, with a raised "CS" on the right side near the receiver extension end.

Its a little confusing.

Its A2 stock construction, but it is shorter like an A1 stock. VERY valuable.

I've never seen one marked, received it on a KAC lower I bought.

How valuable?

It is a "Canadian Short" stock.  They were going for about $200 each last time I checked.  Maybe more today.

He meant $2.00  I will give you 20. .  Seriously, I would love to have one but I would never pay $100 for any AR stock.  That is great you have one and didn't even know what it was.  They are from Colt/Canada or Diemaco made for Canadian Forces.  If you aren't short like me, sell it and buy something you can use.  Some C7 cloner will pay good money for it.

That is a Colt CS stock you are describing.  It was made with the A2 style and material, but is actually A1 length.  They are highly desirable since they have the shorter A1 LOP.  I run CS stocks on both of my fixed-stock A2 rifles.

Wow! I was thinking about removing it and installing a collapsible stock.

Looks like I may have to rethink that.

CS is french/english Court/Short. I have a few of them. They pop up a gun show ever now and then. They did come from Colt on some 9mm Carbines and rifles. I also have some of the A2 butt extension spacer with the longer screws.

Ha ha ha....Not as sexy as the stories above, but CS stocks were found on Colt sporter carbines during the early 1990s leading up into the AWB.  They were on configurations that were not especially sexy due to AWB features such as shaved bayonet lugs and pinned sear blocks.  The CS stocks were removed from these rifles when converted to the evil collapsible stock.  Turns out that many people like the shorter LOP and the Internet folklore of the Canadian SF connection.

Colt even sold a bunch of carbines in the 90's with the same A2 material stock and the A1 LOP without the "CS" on the side.

I have a CS stock. It is sweet. I wish I had more of them.

Congrats, OP.  Those stocks are the cat's ass, and hard to find on purpose.  They're more of a "stumbled upon it" type deal.  

I have them on all of my A2 builds.

While A1 and Cav Arms stocks are the same LOP, you've got the only one with A2/milspec construction.   

It's not internet folklore.  The stocks were made for the Canadian Forces.  When Canada had the C1A1 it was available with short, normal and long buttstocks.  They decided to do the same when adopting the C7.  Canada is bilingual to the extreme.  To the point where the front sight only has an arrow, no up marking and the rear sight had no R for right, just the arrow.

Being pragmatic they adopted only two stocks, the short one is indeed marked CS for court/short as otherwise it would be indistinguishable from a regular A2 unless measured.  The A2 was the default length and if longer was required there was a spacer that installed between the stock and the buttplate.

Now, I can't tell/explain how Colt ended up with so many extra that they put them on factory rifles but they exist because Canada wanted them for their new service rifle in the 80's.  I asked the weapon tech to install one on my issued C7 when I realized how much nicer it felt compared to the standard length.

Thanks Leg!  It is awesome having first hand knowledge on this site.

It's a Canadian tradition that dates back to WWII. It started with the No.4 MkI. Butt stock for No. 4 MkI were available in (B) Bantam, (S) Short, (N) Normal and (L) Long. It continued with the C1A1. C1A1 butt stock came it (S) Short, (N) Normal, (L) Long and (XL) Extra-long.

Can you show images or a Canadian AR with a CS marked stock?

The topic isn't about variations in Canadian stock length.  It is no secret the Commonwealth militaries have a long history of manufacturing rifles with various buttstock lengths (including ARs).

The topic is about CS marked short stocks (the CS is molded into the stock body) that were installed on factory US civilian Colt carbines early into the AWB here in the US.  These short stocks filled the void of the banned evil collapsible stock.

The folklore is the suggestion that CS marked stocks were manufactured and installs on Canadian Spec-Ops weaponry.  That is simply untrue.... it is some garbage a gunshow vendor sells to some sucker in an attempt to squeeze another C-note out their wallet.

I like CS stocks because of the length of pull and quality.  Nothing less.  Nothing more.

Unfortunately I can't show you a pic of the stock in service.  We got rid of all of our fixed stocks in 2004 when we upgraded to the C7A2.  Otherwise I'd just be able to take a pic of my issued rifle since I'd still be using one.

The Colt raised CS stock is one and the same.  A raised S inside the C.  I even managed to get my hands on when when we made the switch.  The wpns tech no longer had a need for them.

These have existed since the mid '80's.  Colt likely produced too many for the contract and simply started using them on factory rifles to get rid of them.  They have a long history of using up military parts on civilian guns once they can't use them on the military guns.  Colt has supplied Diemaco with various parts over the years (and vice versa) when they couldn't meet demand.

The story about SOF is pure bullshit.  These were for every day rank and file.  The idea of special fixed stock for SOF is amusing.  Vendors will continue to ask and receive a premium due to rarity, no bullshit story is required.

Here's a visual reference. These are all the ones I have found at gun shows. One even came off my first 9mm Colt I bought, I swap it out to collapsible stock.