My guess, because its tricky with most scopes such as these and without a picture: £60.
With vintage scopes then condition is everything. 9.8/10 will get a premium, or comes with mounts that look right and in the right position to hide any crimp/ring marks. Anything rough or an "in your face" mark to distract then we are talking pennies.
Nikko Sterling sold in huge numbers. Some were better made than others, but most on the soft side so can collect marks pretty fast. Some had better glass than others, but then there have been so many models and been made for so long.
For a collector then they really do need to look spanking good. I do think any large 1980's collection should have an example of this make, at least somewhere within the collection. Rude not to because a lot of vintage rifles were fitted with them.
Its been a long while since I had one because they were 2nd devision to the best Tasco, B&L, Optima, and Kasnars. I always thought I ought to have had a few when collecting, but somehow never did.
Good luck with the sale.