Art -- there is a fine art to carbine collecting and identification, and the folks over at the gun & knife forums could tell you what every letter, punch prick, and spring on your rifle means and where it came from; I'm still a newbie, but I've got some books
. Your rifle is an Inland, which is one of about 10 WWII manufacturers of carbines, and also the most common (Inland made 2.6 million carbines from 1942 - 1945, or 43% of the wartime production). Underwood was another, along with IBM (believe it or not), Rock-Ola (a jukebox maker), and several others. After WWII, the vast majority of carbines were rebuilt at various military armories across the country, and broken or worn out parts were replaced from spares and parts off of other rifles. Hence, many rifles have a mixture of parts from various manufacturers. I imagine that's how your rifle came to be. Many of the armory rebuilt rifles saw service in Korea. Many others were lent to various foreign countries during the cold war, and those that were reimported also bear an additional stamping from the importing company (Blue Sky, e.g.).
If you strip the rifle down, every part should have various letters stamped on it, and a good collector could tell you who made each of those (most of the Inland parts are stamped I or AI, BI, PI, etc.). The stock markings should tell you its history. If it doesn't have any stampings at all, it's not a GI stock.
I'm not sure what the muzzle device you have is -- does it attach with a thumb screw? If it's not a cone-shaped flash hider or a grenade launcher (cylindrical and about 6 inches long with circular rings milled into the surface), I don't know what it is. No bayo lug means that you have an earlier barrel band (they didn't have them initially), but this doesn't fit with the rifle being armory rebuilt (they usually updated all of the rifles when they rebuilt them).
If your carbine isn't a reimport it may still be worth a decent amount of money even though it's all mixed up. Armory-rebuilt carbines in good condition are going for at least $500, although I'm not the best person to give you accurate pricing. Don't part with it for cheap without checking, though; if it's an heirloom, you probably don't want to sell it anyway.
Carbines are very interesting and kind of addictive -- have fun.
Andrew