Have just bought a Nikko Stirling Mountmaster 6x42AO for my Stingray.
It only cost £37 from Uttings.
Its very well made and well constructed, everything turns and twists smoothly without grating or grinding,
The scope comes with lens covers and a set of excellent quality two piece, double screw mounts with an arrestor hook.
The optics are bright with a sharp, contrasty image.
It comes with nicely spaced mildots.
It also has Adjustable Objective for paralax control.
I can highly recommend this scope for the price.