particular person, for his purposes only, and on its face not intended to be shown to or relied upon by anyone else. Consequently no one else may invoke an estoppel.[1] When, therefore, the addressee assigns or puts up the letter as security, the only legal right of the pledgee would seem to be a right to the possession of the paper. Without the paper, the addressee cannot enforce his rights against the issuer nor negotiate bills. Thus the right of possession of the paper is a valuable one and by its mere possession the pledgee is in a position to exert pressure upon the pledgor for his security. The case is legally like the deposit of title deeds in English law,[2] and suggests the question whether the pledgee of a letter of credit obtains any lien in equity. But what has the addressee-pledgor to give him? Certainly he has nothing in praesenti on any of the theories considered.
Turning to the theory of the letter as an acknowledgment of money received and held to the use of addressee, we get a like re- sult. True, in an ordinary case of money had and received, there is a debt enforceable in a money count, which debt may be assigned. But here the money is held to the use of the addressee upon condi- tion and there is no assignable debt until the condition is performed. Nor is the result different upon a theory of the letter as an instru- ment of the law merchant. For the letter by its very terms does not contain a power of negotiation as in the case of commercial paper payable to order or bearer. Consequently the position of the assignee for security seems to be simply that of one who for his security has possession and right of possession of a document with- out which the pledgor thereof cannot realize a valuable possibility. When the possibility has come to fruition in an actual claim in praesenti, equity might then consider the pledgee of the letter an equitable lien-holder.[3] But this could scarcely happen without the production of the instrument, so that possession of it and consequent control of the situation is the pledgee's real security. In a case like Krakauer v. Chapman [4] the theory of money held by the issuer to the use of the addressee would be advantageous to the
pledgee. If the addressee may sometimes have a claim against the
