In searching for a particular pattern of Imperial Glass, I have increasingly noticed that certain trademarks used by the Imperial Glass Company, as well as some patterns, are being confused with each other. As an example, Nucut vs. IG. 

The Nucut trademark was in use from as early as 1911 to around 1932 when it was removed from all moulds.  The I super-imposed over the G or IG was in use from around 1951 to the early 1970's. The main difference between these trademarks is, of course, the timeline.  The pieces marked with IG will also, more often than not, be a pattern reissue or reproduction.  This could greatly influence the value of the piece.  If someone claims to have an Imperial Glass Nucut piece marked with the IG, IT IS NOT NUCUT.  It is simply Imperial Pressed or Pattern Glass from the 50's to 70's period.

Nucut isn't a pattern name. It's a LINE name used to identify a variation in the company's pressed glass which made it look and feel more like cut glass with sharper points and edges. There are several different patterns produced with the Nucut mark.  I must also point out that the Imperial Glass Company did not consistently mark the pieces so there is a certain amount of trust one must have that the sellers know what they're selling and are honestly presenting their wares.

I have also come across some information about a particular book used for pattern identification.  Apparently  the "Standard Encyclopedia of Pressed Glass 1860-1930" by Edwards and Carwile is frought with mistakes.  If any of you (buyers or sellers) are using this book, I would like to suggest switching to a different one. You can go to patternglass.com and click Granny's Pointers and Pitfalls.  Then under the Pointers heading click "see corrections."  The list of corrections is fairly extensive.  I hope this guide will be helpful and the following are some other sites that may prove useful: imperialglass.org and ddoty.com.