Si,hai raggione l'avevo visto ma cercavo con il termine receipt accanto. L'ho trovato ora... ed è un termine usato dai truffatori!
Safekeeping Receipt = International Depository Receipt (IDR):
A negotiable, bank-issued certificate representing ownership of stock securities by an investor outside the country of origin. An international depository receipt, or IDR, is the non-US equivalent of an American Depository Receipt. These instruments have been used since the 1970's to facilitate international trading in securities. The securities backing the receipt remain in the custody of the issuing bank or a correspondent [bank].
The Scam: In the swindler's world, an IDR or ADR is called a Safekeeping Receipt. The swindler uses the term to convince you that funds can be exchanged for a Letter of Credit or PRIME BANK GUARANTEE that will be kept by the TRADING BANK (there's no such thing the way swindlers use the term).
In return, the "trading bank" will issue a safekeeping receipt for the guarantee. Then the "trading bank" puts the original safekeeping receipt in safekeeping and issues a second safekeeping receipt for the first one.