You do not mention the size or dollar amount you paid which would be helpful ,but let me give you some clues.
Estate sales attract many professionals in the field who are savvy on values. If you were able to buy it for a very inexpensive amount the odds of it being solid gold are unlikely , particularly if it has a japan marking. I have not seen any solid karat gold japan cherubs.
A certified gemologist found at a jewelers can tell you if it is real gold. If it is, it would be valuable.
Many antique or vintage pieces are heavy but are made of pot metal , paris plaster, and other alloys so weight is not an indicator one way or another.
There are sites on line that offer appraisals by filling out a form and sending a picture, for example www.instappraisal.com.
You enter known info about the piece,send a photo , and you get back an expert appraisal for $17.95.
I will assist you further for no additional charge if you can provide more detail.
One other thing I want to mention. The auctioneers and relatives normally know if a piece is valuable so it is difficult to "steal " a valuable piece no one else knew about or bid on.
However, I love cherubs too and every estate sale I went to I bought them so at least you have a beautiful cherub to start a collection with, and sometimes the beauty makes the value irrelevant.
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Evie