Commercial overprints can be found on values higher than the 1d or 2d postage stamps used for receipts.
6d stamps were used to pay the duty on hire purchase agreements or insurance policies.
1/- stamps were used on whole life insurance policies and notarial acts.
Overprinted 1/- stamps are scarce but the 6d value stamps are more common as they were used by retail firms, electricity and gas companies as well as the insurance companies.
By Herbert Vogelsang