1937 multi taxed airmail envelope from Leiden, addressed to Singapore and redirected to Hong Kong. Straits Settlements 1924 12c postage due tied 'SINGAPORE' c.d.s. '18 MY 1937' and on the reverse Hong Kong 10c pair and a single 6c tiedd 'VICTORIA' c.d.s. '5 JU 37' An attractive combination of postage dues.