Grade And Value Of This Half Sovereign

I agree with Mr T with Fine.
The halves coins saw much more circulation than sovereigns of equivalent date.
The sovereigns were much more used for international payment as bullion, mainly to India, whereas the halves were made for local circulation.
That is why far fewer halves were minted, and why their average condition for date is much poorer.

A perusal of a catalogue showing mintage figures for dates and mints, and values for condition bears these facts out.

Which book are you using Dawn62? The above coin is no British and doesn't appear in my Collectors' Coins Great Britain. And where do you see the mint mark? Sovereigns and half sovereigns with that reverse didn't have mint marks to my knowledge.

It's a type one obverse anyway. It looks like a type 3 reverse which is the most common and McDonalds gives it a value of $1250.

Very obviously, Sydney Mint sovereigns and half sovereigns of 1855 to 1870 don't need a mint mark. The name of the Mint is part of the legend on the reverse.
They have exactly the same specifications in every respect as the equivalent British gold coins of the same period.