The British monetary system makes sense to many people, but it's pretty complicated if you ask me. In 1970 they changed, but before then there were four farthings in a penny. The plural of penny is pence, and there were 12 pence in a shilling. Two shillings make a florin and five shillings make a crown. Four crowns add up to one pound, which is also called a sovereign. And, just to round things out, 21 shillings make a guinea.
So, um, one-third farthing is 1/144th of a shilling and it takes 3024 one-third farthings to make a guinea.
Now, back to business. Here are some typical catalog values for 1/3 farthings dated between 1866 and 1885:
worn: $3 US dollars approximate catalog value
average circulated: $8
well preserved: $50
fully uncirculated: $140
Actual value will be less, as explained on our Terminology page.
All the dates in this series are about equal in collector value.