The Collaborative International Dictionary of English v.0.48:
Subtreasury \Sub*treas"ur*y\, n.; pl. Subtreasuries. A subordinate treasury, or place of deposit; as, the United States subtreasury at New York. [U. S.] [1913 Webster]WordNet (r) 3.0 (2006):
subtreasury n 1: a subordinate treasury or place of deposit