two memorandums from the Commissioner of Estate Duties to Zehnder Brothers (solicitors), enclosed with receipts (numbered 6446 and 6489) for payment of estate duty, dated 9 November 1940 and 2 December 1940; letter to the Commissioner of Estate Duties, dated 8 November 1940, regarding estate duty payment of $5623.77 by Cheang Seok Hean Neo, Cheang Seok Chin Neo and Cheang Seok Cheow Neo; and a certificate on payment of estate duty issued by the Commissioner of Estate Duties, numbered 206/1940 and dated 3 December 1940.