As a general rule COA for coins are worth 2%-7% of the coin value. The 2% for expensive coins and 7% for cheaper coins or for coins that were packaged by telemarketers with no COA included. Some sample pricing for COAs that I have sold over the year, coin prices are for 69 quality.

$1200 1981 Bronze age gold set, single COA, set price $30000, so 4%

$75 1983 27g silver panda, single COA, coin price $2000, so 3.7%

$100 1983 15g silver pig, single COA, coin price $3000, so 3.3%

$20 1988 1oz silver dragon, single COA, coin price $400, so 5%

$1000 1992 I&D gold set of 5, 5 COAs, set price $40000, so 2.5%

$250 1992 I&D silver piefort set of 5, 5 COA, set price $7000, 3.6%

$200 1994 gold panda proof set of 5, single COA, set price $9000, so 2.2%

$220 1995 1oz gold panda proof, single COA, coin price $11000, so 2%

$30 1996 1oz silver panda proof, single COA, coin price $450, so 6.6% (cheap coin, percentage is higher)

$300 2000 scallop gold dragon, single COA, coin price $5000, so 6% (this coin was included in telemarketed set with 5oz silver dragon)

For the Peking opera, I would estimate the COA is probably worth 2% of the coin's value, so about $600-$900, however, I would recommend you put it on eBay for $1000 best offer and over the course of a year you may end up selling it for $400-$1000, if you want to sell it in a rush, just put it up as auction starting price $0.88 and let it go for whatever the market brings, it could go for $100-$400 in an ebay auction. Good Luck.

Arif