These coins catalogs as follows:
worn: $10 US dollars approximate catalog value
average circulated: $22
well preserved: $50
fully uncirculated: $150
Sixpence dated 1887 are a little more common, so prices go down by a factor of two, approximately.
Now, here is the exciting coin in this series: the 1893 sixpence with the portrait of Queen Victoria that looks like the one on this page. There are other 1893 sixpence, but if you find one as shown, figure catalog values as:
1893 SIXPENCE (must look like the picture on this page):
worn: $300 US dollars approximate catalog value
average circulated: $500
well preserved: $1500
fully uncirculated: $3000
The 1893 sixpence on this page sold for $326 US dollars during a 2009 auction by Spink. It would probably sell for more today.