An "Ox" is simply a cow that has been trained to pull farm implements and wagons, or as Wikipedia says "an ox is nothing more than a mature bovine with an 'education'."
This 50-bututs ox reverse first appeared in 1971 (KM12, one year only), then was reissued with the coat of arms reverse, again for one year only (KM58).
All coin images in Daniel's Coin Zoo are from my personal collection. I collect, research, and personally photograph every coin displayed on this site. PLEASE do not take my images without permission. If you would like to use any coin image you see, just ask me. Thank you.