Your commemorative plate from 1971 by Spode for the 2500 Years of Persian Monarchy approved by Pahlavi sells for a high average of $400 on today's market.
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Having the original packaging and papers does help sale-ability raises perceived value. The highest auction sale price I found on the 10,000 limited edition plate was $550 in 2009. Since then the sale mode at auction is currently $400. There is another version of the plate by Spode in a limited edition of only 2000 that sold for $2800 at auction in 2013: http://www.worthpoint.com/worthopedia/iran-imperial-plate-persia-spode-416943681
Yes it is. Though it may sound cliche, the best platform for you to sell these is on Ebay. It is where the most potential buyers from all over the world would first go to search for such items.