This is Plate #6 from the "Forbidden City" series, titled "The Court from Behind the Screen" (垂帘听政 - Chuí Lián Tīng Zhèng).

Here are the specific details translated and transcribed from the back of your plate:

Item Specifications

• Year of Release: 1991

• Unique Limited Edition Number: 甲五〇〇四 (Serial Number: A5004)

• Artist: Shen Fu (沈浮)

• Plate Title: 垂帘听政 (Literally translated as "Ruling from Behind the Curtain" or "The Court from Behind the Screen," a famous historical practice during the Qing Dynasty).

• Production Run Limit: The text notes that production was strictly limited to 150 firing days.

Having the Certificate of Authenticity (COA) and original box intact is excellent news because it helps preserve the maximum resale potential for vintage collector plates. 

Current Valuation

Individual plates from the Forbidden City series by Imperial Jingdezhen Porcelain generally value as follows:

• Single Plate with COA: Individual plates typically sell for $20 to $45 USD on platforms like eBay and Mercari.

• Full Set Value: If you own the entire 8-plate set complete with all boxes and COAs, the bundle value can rise to around $150 to $250+ USD. 

What the COA Verifies

Your certificate acts as formal proof that the plate belongs to a limited-edition run authenticated by The Palace Museum of Beijing and crafted using fine hard-paste porcelain from the historical kilns of Jingdezhen, China. 

Individual plates from the 1991 Imperial Jingdezhen "Forbidden City" series generally value between $25 and $55.