First Time Posting Here - I've Bought A .303 But What Scope Is This?

[mrclark303]

Hello all, thanks for adding me to the group.
I've recently fallen completely in love with .303's after a friend showed me his Mk4.
I felt an instant bond with the rifle and sat cradling it for a good length of time before reluctantly handing it back. I have since been drawn to every .303 I have seen when travelling to gun shops and shows with him.
Needless to say, most I've seen are far out of my budget, so when I did find one cheap at a local gun store I instantly put it on payment plan. I'm still paying it off but wanted to know if anyone can help identify the scope as this doesn't look like anything I've seen on other .303's I've seen elsewhere?
So far by searching on line I've identified it as a Central (Australia) No 4 scope but I have no idea about the additional piece with the optical lens?
I'm very curious about it.
Thanks

Welcome aboard mate, in all it's variants, its the rifle of the commonwealth and our fathers and forefathers ...

You had your free hit, with your friends rifle, unfortunately you are now hooked and there is no known cure!

Prepare to spend money and really enjoy yourself....