Ya Wan Zhen Cang porcelain horse

This piece was my grandmothers and that's about all I know. After a lot of google searching I found the symbol on the bottom was Ya Wan Zhen Cang, and that it's probably mid 20th century. That's all I could find on it and the only other pieces I found by that manufacturer were plates and vases, no other horses. There were two pieces for sale on ebay, one for $23 and another for $899 so I have no clue how much this would be worth (or if it's even worth anything). I'm also wondering what the recessed circle in the horse's back is for. Any info or appraisal price would be much appreciated!