Thanks guys. I must have the non AN glass as neither the top or bottom glass has any texture to it.

I found some more information and other options over on dursts webpage:

http://durst-pro-usa.com/neg_glass.htm
And a couple interesting statements:

-We still offer the old type AN (Anti Newton) glass for those customers who print with COLD LIGHT and DIFFUSED LIGHT sources. But would like to point out that AN glass deteriorates sharpness considerably. The rate of deterioration is so considerable that Durst Auto Focus enlargers can not be programmed for correct focus using Anti Newton Glass
-The new AR glass will also suppress Newton rings.

-Also the trend is that Fine Art printers now are using a glass less mask on top of the negative and only glass at the bottom.

So, replacing the glass is an option...or try the mask technique as noted above as top layer.

Anyway, alot more confusing than I would've thought regarding keeping a large 4x5 neg. flat for enlarging.

Chris

ps anyone know the website of Omega enlargers? I thought it was simmons omega, but can't find the company's webpage and Ive been there before! geesh.