Neville, this is an interesting plate. I looked through “Die Wapen van die Suid Afrikaanse Republiek” (Dr. Coenraad Beyers, undated) and many of the images have eagles facing left, and/or show short wings. The image most resembling the emblem on your plate is actually the official ZAR Groot Zegel and specifically the one used for Kruger’s sash and coach.
The official colours of the ZAR emblem are: Gules (Red), Azure (Blue), Sable (translated as black but should be Sand) Vert (Green), Purpure (purple), Silver (white in pictures) and Gold (yellow in pictures). There is no mention of Brown but all other colours on the plate are correct.
The plate itself looks run-of-the-mill and hopefully some crockery expert can identify the producer/country of production. The (I presume) hand painting was applied in a manner that suggests use rather than display, and my guess is that the plate was part of a larger dinner service for use in a consulate or, probably more likely, for official events in the ZAR.