What's the difference beween NASD and NSDQ in Level II?

Hi all,

I am using Sterling platform and I am a little confused with NASD and NSDQ in the Level II window,
as you can see in the attatched picture, most of the time, the quotes from NASD and NSDQ are almost the same,
however, they appear as two different ecns.

Does anyone know what's the relationship (or difference) beween NASQ and NSDQ? Also should I filter out
one of them in order to aovid double counting?

Thanks.

 

haha,I don't know either,
it's fantastic to find such a place to learn from you americans

 

I believe NSDQ is the symbol for the Nasdaq SuperMontage.

http://www.stockwatch.com/stocks/stocks_helper.aspx#exchangecodes

(Search for "NSDQ")

I don't know what NASD is. Maybe a market maker?

I use RealTick and Schwab's StreetSmart Pro and have only seen NSDQ in level II.