I see a lot of mis-listed items on ebay because a seller doesn't know their markings.  Many are new sellers, so I thought just a few basics for the markings you may run across would be helpful to both the buyer and the seller.  I noted that one seller already addressed the Fire-King vs Federal marking, but I will go over that one again also.

Let's start with Federal.  Their marking is an F in a shield.  They have no connection with Fire-King.  Fire-King does not have a "marking" so to speak, they will always use the full name on marked pieces.  And yes, there are unmarked pieces of Fire-King.

Another one I see a lot of on listings is a seller will say a piece is an old Anchor Hocking piece, marked with the AH.  What you really have is a large H over the A.  The marking for Hazel Atlas.  Anchor Hocking will either used the full name, or the anchor mark with or with out the H, it depends on the era. 

Now, that funny looking I through the G....It's not Indiana!  It stands for Imperial Glass, it was the marking they used from the 50's to the early 70s.  I have never seen a piece Indiana Glass with a marking.  [If you ever come across one, I want to see it please!!]  :)

Libbey uses a stylized cursive L, often in a circle.  Sometimes the marking doesn't look right unless you look down into the glass.  I don't often see misuse of this marking, but thought I would add it in. 

The last one I am going to mention for now is Heisey.  I have on rare occasion seen this listed as Anchor Hocking.  The marking for Heisey was an H inside diamond. 

I hope this helps those new to ebay, or just new to the crazy world of glassware!