There is a lot of information about antiques online, but sometimes the info we seek is just not there. You may try Gotheborg.com or the International Nippon Collectors Club (who may be able to steer you in the right direction.)
Sometimes, we just have to contact a professional. You can take your set to an antique dealer who specializes in similar goods or find an appraiser in your area. Either will charge a fee. Ask what they charge before you take the set to them. Make sure you have photographs of the set.
You might call your insurance broker for a reference. As people insure valuables like antiques, your broker will probably know someone who can help you.