Chile 1860 British PO Valparaiso via Panama to New York Stampless Steamship SFL

Stampless folded letter, with contents, postmarked on back with British Post Office VALPARAISO double split-ring (Nov 18), Panama “A” double split-ring (Dec 6) on front, to New York, struck with fine two-line “PAID TO / PANAMA” in red and black circular “Steamship /10” due marking, a lovely and fresh cover; ex Brian Moorhouse Estate.