I have noticed there are 2 distinct type of coriander seed -
1 - round light brownish seed
2 - oval greenish seed
The round seeds I believe originate from Russia and are of very poor quality imo
The oval seeds are pukka Indian seeds and are far superior (wonderful aroma)
so watch what u buy - I ended up with a load of the poor quality seed bought from an online spice store, now I only buy spices from my local asian grocer. Look on the packet "produce of India" are the magic words.

Kev.