Nice coin, townfan --
These old shillings can be quite valuable, especially if in well-preserved numismatic condition. Your 'heavily worn' description means yours will be worth small amounts.
Just about all of these shillings betwee 1838 to 1887 command catalog values as follows:
SHILLING: MOST DATES
worn: $20 US dollars approximate catalog value
average circualted: $80
well preserved: $250
fully uncirculated: $600
The coin in the picture in worn condition, so its catalog value would be about $20.
There are a few 'good dates' in the series, and these can be real winners. In the list below, the value after the date is catalog value in well preserved condition. Worn coins are worth considerably less.
SHILLING: BETTER DATES
Don't forget these are catalog values for coins with scratches, spots, stains, cleanings, nicks, gouges, and the like. Read our Important Terminology page to properly interpret catalog values.