"Intervening prices"

Dear teachers

What does 'Any intervening prices available on request' mean exactly in a Christmas sale scenario? I have abusolutely no idea at all.

Thanks in advance.
Guoguohu

It appears to make no sense. Have you more context?

5jj said:

It appears to make no sense. Have you more context?

Click to expand...

I was in Marks & Spencers, noticing this small print on many 'sales 50% off' boards.

G