The three impressed 'Wedgwood' Blue jasperware round medallions (mounts)

I had trouble identifying specifically who these figures are.  I would say definitely greek Mythology.

Most likey POSEIDON, AMPHITRITE & TRITON.  

I am not sure how to date these but i believe they are antique age.  I have not seen similar ones so I would also assume they are rare.  If you can identify or have any info that woulf be helpful  (even if you are not interested in purchasing) I would so appreciate it.  :)