http://www.gunsamerica.com/guns/976483151.htm

I've got the same thing with a slightly lower serial.  Is it really worth what this guy is asking?  

Its plenty high but not completely out of line.  Kind of a rare variation.  Would need to examine closer to check condition, rebuild marks, etc.  

Carbine prices are just plain nutty and have been for a few years.  Figure a decent non-import rebuild will start in the mid $600 range and then climb from there.  IBM/AO is certainly out of the ordinary, so no, the price isn't out of line.

Quoted: Its plenty high but not completely out of line.  Kind of a rare variation.  Would need to examine closer to check condition, rebuild marks, etc.   Carbine prices are just plain nutty and have been for a few years.  Figure a decent non-import rebuild will start in the mid $600 range and then climb from there.  IBM/AO is certainly out of the ordinary, so no, the price isn't out of line.

Crazy.  Grandaddy bought it mail-order thru the NRA back in the early '60s for $19.95.  I haven't been paying attention-seems like last time I looked carbines were going for $450-500.

Any obvious marks I could look for?  Only marks I see are an "H" on the rear sight, an "M" on the mag release, and a "W" on the...hmm...the metal part attached to the stock behind the reciever.  The rifle's in probably 95% condition, but the stock isn't original.  

All the parts will have a mark of some kind.  The list of what the various marks means runs into dozens of pages.  Check the stock in the wrist area.  Rebuild marks, typically a two or three letter code, will appear there.  Look for the crossed cannons ordnance mark in about the same place.  Barrel should have a date and manufacturer stamped on it towards the muzzle. And on and on.  

Lots of variation in carbines.  Twelve major contractors (only one of which made guns before the war), hundreds of subcontractors.  A fascinating subject to study.  And one with few absolutes.  Almost anything is possible in the world of carbines.  

If you can find the documentation that came with the carbine from the NRA you have indeed struck gold.

I think that price is very high. Ive seen other IBM/AO reveiver based carbines in the $600-$700 range. I bought mine a couple yrs ago for $600 and change w/ an IBM bbl and bolt. Id keep looking around if I was you. If youre really interested Id make very certain that bbl band is a real type 1.