Do remember that what is very common in Manchester or London, like old One Pound Notes or even Discount or Savings Stamps, like the old Green and Pink Shield Stamps may be very common in the UK, but a collector on the other side of the world might be willing to pay a few dollars for what in the UK might cost only a few pennies.
Of late my best trade has been in quite common Russian banknotes, but here they are very common, not so perhaps in the UK or US.
You may not make a fortune but there is always a little profit in such items.
Keep you eyes open and do have a rummage in all those places you have not looked in for years
